We use asexual development of Neurospora crassa as a model system with which to determine the causes of cell differentiation. Air exposure of a mycelial mat induces hyphal adhesion, and adherent hyphae grow aerial hyphae that, in turn, form conidia. Previous work indicated the development of a hyperoxidant state at the start of these morphogenetic transitions and a large increase in catalase activity during conidiation. Catalase 3 (CAT-3) increases at the end of exponential growth and is induced by different stress conditions. Here we analyzed the effects of cat-3-null strains on growth and asexual development. The lack of CAT-3 was not compensated by other catalases, even under oxidative stress conditions, and cat-3(RIP) colonies were sensitive to H(2)O(2), indicating that wild-type (Wt) resistance to external H(2)O(2) was due to CAT-3. cat-3(RIP) colonies grown in the dark produced high levels of carotenes as a consequence of oxidative stress. Light exacerbated oxidative stress and further increased carotene synthesis. In the cat-3(RIP) mutant strain, increased aeration in liquid cultures led to increased hyphal adhesion and protein oxidation. Compared to the Wt, the cat-3(RIP) mutant strain produced six times more aerial hyphae and conidia in air-exposed mycelial mats, as a result of longer and more densely packed aerial hyphae. Protein oxidation in colonies was threefold higher and showed more aerial hyphae and conidia in mutant strains than did the Wt. Results indicate that oxidative stress due to lack of CAT-3 induces carotene synthesis, hyphal adhesion, and more aerial hyphae and conidia.

In mammals, methionine adenosyltransferase (<em>MAT</em>), the enzyme responsible for S-adenosylmethionine (AdoMet) synthesis, is encoded by two genes, <em>MAT</em>1A and <em>MAT</em>2A. In liver, <em>MAT</em>1A expression is associated with high AdoMet levels and a differentiated phenotype, whereas <em>MAT</em>2A expression is associated with lower AdoMet levels and a dedifferentiated phenotype. In the current study, we examined regulation of <em>MAT</em>2A gene expression by l-methionine availability using HepG2 cells. In l-methionine-deficient cells, <em>MAT</em>2A gene expression is rapidly induced, and methionine adenosyltransferase activity is increased. Restoration of l-methionine rapidly down-regulates <em>MAT</em>2A mRNA levels; for this effect, l-methionine needs to be converted into AdoMet. This novel action of AdoMet is not mediated through a methyl transfer reaction. <em>MAT</em>2A gene expression was also regulated by 5'-methylthioadenosine, but this was dependent on 5'-methylthioadenosine conversion to methionine through the salvage pathway. The transcription rate of the <em>MAT</em>2A gene remained unchanged during l-methionine starvation; however, its mRNA half-life was significantly increased (from 100 min to more than 3 h). The effect of l-methionine withdrawal on <em>MAT</em>2A mRNA stabilization requires both gene transcription and protein synthesis. We conclude that <em>MAT</em>2A gene expression is modulated as an adaptive response of the cell to l-methionine availability through its conversion to AdoMet.

BACKGROUND

falls are a common cause of injury and decreased functional independence in the older adult. Diagnosis and treatment of fallers require tools that accurately assess physiological parameters associated with balance. Validated clinical tools include the Berg Balance Scale (BBS) and the Timed Up and Go test (TUG); however, the BBS tends to be subjective in nature, while the TUG quantifies an individuals functional impairment but requires further subjective evaluation for balance assessment. Other quantitative alternatives to date require expensive, sophisticated equipment. Measurement of the acceleration of centre of mass, with relatively inexpensive, lightweight, body-mounted accelerometers is a potential solution to this problem.

OBJECTIVE

to determine (i) if accelerometry correlates with standard clinical tests (BBS and TUG), (ii) to characterise accelerometer responses to increasingly difficult challenges to balance and (iii) to characterise acceleration patterns between fallers and non-fallers.

METHODS

torso accelerations were measured at the level of L3 using a tri-axial accelerometer under four conditions; standing unsupported with eyes open (EO), eyes closed (EC) and on a mat with eyes open (MAT EO) and closed (MAT EC). Older patients (n = 21, 8 males, 13 females) with a mean age of 78 (SD +/- 7.6) years who attended a day hospital were recruited for this study. Patients were identified as fallers or non-fallers based on a comprehensive falls history.

METHODS

Spearman's rank correlation analysis examined the relationship between acceleration root mean square (RMS) data and the BBS while Pearson's correlation was used with TUG scores. Differences in accelerometer RMS between fallers and non-fallers and between test conditions were examined using t-test and non-parametric alternatives where appropriate.

RESULTS

there was a stepwise increase in accelerometer RMS with increasing task complexity, and the accelerometer was able to distinguish significantly between sway responses to all test conditions except between EO and EC (P < 0.05). Acceleration data for MAT EO were significantly and inversely correlated with BBS scores (P = -0.829, P < 0.001) and positively correlated with TUG values (r = 0.621, P < 0.01). There was a significant difference in acceleration RMS for MAT EO between fallers and non-fallers (P < 0.011).

CONCLUSIONS

this is the first study of its kind to show a high correlation between accelerometry, the BBS and TUG. Accelerometry could also distinguish between sway responses to differing balancing conditions and between fallers and non-fallers. Accelerometry was shown to be an efficient, quantitative alternative in the measurement of balance in older people.

Laminated mats of unique character in siliceous alkaline hot springs of Yellowstone Park are formed predominantly by two organisms, a unicellular blue-green alga, Synechococcus lividus, and a filamentous, gliding, photosynthetic bacterium, Chloroflexus aurantiacus. The mats can be divided approximately into two major zones: an upper, aerobic zone in which sufficient light penetrates for net photosynthesis, and a lower, anaerobic zone, where photosynthesis does not occur and decomposition is the dominant process. Growth of the mat was followed by marking the mat surface with silicon carbide particles. The motile Chloroflexus migrates vertically at night, due to positive aerotaxis, responding to reduced O(2) levels induced by dark respiration. The growth rates of mats were estimated at about 50 mum/day. Observations of a single mat at Octopus Spring showed that despite the rapid growth rate, the thickness of the mat remained essentially constant, and silicon carbide layers placed on the surface gradually moved to the bottom of the mat, showing that decomposition was taking place. There was a rapid initial rate of decomposition, with an apparent half-time of about 1 month, followed by a slower period of decomposition with a half-time of about 12 months. Within a year, complete decomposition of a mat of about 2-cm thickness can occur. Also, the region in which decomposition occurs is strictly anaerobic, showing that complete decomposition of organic matter from these organisms can occur in the absence of O(2).

To better understand the epidemiology and population structure of Cryptococcus neoformans, we determined mating types for 358 C. neoformans strains isolated through the active surveillance program from 1992 to 1994 in four geographic areas in the United States: San Francisco, California; Georgia; Texas; and Alabama. Two assays were used to determine mating types: (i) crossing with standard laboratory tester strains JEC20 and JEC21 on V8 agar medium; and (ii) PCR with the mating type alpha allele-specific primer of the STE12 gene and with serotype (A and D)- and mating type (a and alpha)-specific primers of the STE20 gene. Using these two methods, we found that this sample consisted of the following: (i) 324 serotype A, mating type (MAT) alpha (Aalpha) strains; (ii) 12 serotype D, alpha (Dalpha) strains; (iii) 14 serotype AD strains with mating type alleles Aa and Dalpha (AaDalpha); (iv) 2 serotype AD strains with mating type alleles Aalpha and Da (AalphaDa); (v) 3 serotype B, alpha (Balpha) strains; and (vi) 3 serotype AD strains but with only one mating type allele. No strain with MATa was found within serotype A, B, or D in this collection. Interestingly, 14 of the 19 serotype AD strains contained the Aa allele at the STE20 locus; 13 of these 14 were from San Francisco. Our results suggest that the environment in San Francisco might contain Aa strains capable of mating with Dalpha strains. In addition, our result demonstrate that the sample from San Francisco had a significantly higher proportion of self-fertile strains than those from the other three areas.

Biocompatible carboxyethyl chitosan/poly(vinyl alcohol) (CECS/PVA) nanofibers were successfully prepared by electrospinning of aqueous CECS/PVA solution. The composite nanofibrous membranes were subjected to detailed analysis by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). SEM images showed that the morphology and diameter of the nanofibers were mainly affected by the weight ratio of CECS/PVA. XRD and DSC demonstrated that there was strong intermolecular hydrogen bonding between the molecules of CECS and PVA. The crystalline microstructure of the electrospun fibers was not well developed. The potential use of the CECS/PVA electrospun fiber mats as scaffolding materials for skin regeneration was evaluated in vitro using mouse fibroblasts (L929) as reference cell lines. Indirect cytotoxicity assessment of the fiber mats indicated that the CECS/PVA electrospun mat was nontoxic to the L929 cell. Cell culture results showed that fibrous mats were good in promoting the cell attachment and proliferation. This novel electrospun matrix would be used as potential wound dressing for skin regeneration.

Toxoplasma gondii, Neospora caninum, Sarcocystis neurona, and S. canis are related protozoans that can cause mortality in many species of domestic and wild animals. Recently, T. gondii and S. neurona were recognized to cause encephalitis in marine mammals. As yet, there is no report of natural exposure of N. caninum in marine mammals. In the present study, antibodies to T. gondii and N. caninum were assayed in sera of several species of marine mammals. For T. gondii, sera were diluted 1:25, 1:50, and 1:500 and assayed in the T. gondii modified agglutination test (MAT). Antibodies (MAT>> or =1:25) to T. gondii were found in 89 of 115 (77%) dead, and 18 of 30 (60%) apparently healthy sea otters (Enhydra lutris), 51 of 311 (16%) Pacific harbor seals (Phoca vitulina), 19 of 45 (42%) sea lions (Eumetopias jubatus) [corrected] 5 of 32 (16%) ringed seals (Phoca hispida), 4 of 8 (50%) bearded seals (Erignathus barbatus), 1 of 9 (11.1%) spotted seals (Phoca largha), 138 of 141 (98%) Atlantic bottlenose dolphins (Tursiops truncatus), and 3 of 53 (6%) walruses (Odobenus rosmarus). For N. caninum, sera were diluted 1:40, 1:80, 1:160, and 1:320 and examined with the Neospora agglutination test (NAT) using mouse-derived tachyzoites. NAT antibodies were found in 3 of 53 (6%) walruses, 28 of 145 (19%) sea otters, 11 of 311 (3.5%) harbor seals, 1 of 27 (3.7%) sea lions, 4 of 32 (12.5%) ringed seals, 1 of 8 (12.5%) bearded seals, and 43 of 47 (91%) bottlenose dolphins. To our knowledge, this is the first report of N. caninum antibodies in any marine mammal, and the first report of T. gondii antibodies in walruses and in ringed, bearded, spotted, and ribbon seals. Current information on T. gondii-like and Sarcocystis-like infections in marine mammals is reviewed. New cases of clinical S. canis and T. gondii infections are also reported in sea lions, and T. gondii infection in an Antillean manatee (Trichechus manatus manatus).

OBJECTIVE

Opioid use disorder (OUD) is a substantial public health problem. Buprenorphine is an effective medication-assisted treatment (MAT) for OUD, but access is difficult for patients, especially in rural locations. To improve access, the Comprehensive Addiction and Recovery Act of 2016 extended the ability to get a Drug Enforcement Administration (DEA) waiver to prescribe buprenorphine to treat OUD to nurse practitioners (NPs) and physician assistants (PAs). This study summarizes the geographic distribution of waivered physicians, NPs, and PAs at the end of 2017 and compares it to the distribution of waivered physicians 5 years earlier.

METHODS

Using the DEA list of providers with a waiver to prescribe buprenorphine to treat OUD and the Area Health Resources File, we assigned waivered providers to counties in 1 of 4 geographic categories. We calculated the number of counties in each category that did not have a waivered provider and county provider to population ratios and then compared our results to the waivered workforce in 2012.

RESULTS

The availability of a physician with a DEA waiver to provide office-based MAT has increased across all geographic categories since 2012. More than half of all rural counties (56.3%) still lack a provider, down from 67.1% in 2012. Almost one-third (29.8%) of rural Americans compared to 2.2% of urban Americans live in a county without a buprenorphine provider. NPs and PAs add otherwise lacking treatment availability in 56 counties (43 rural).

CONCLUSIONS

Overall, MAT access has improved, but rural communities still experience treatment disparities.

The metabolic activities of microbial mats have likely regulated biogeochemical cycling over most of Earth's history. However, the relationship between metabolic activity and the establishment of isotopic geochemical gradients in these mats remains poorly constrained. Here we present a parallel microgeochemical and microbiological study of micron-scale sulfur cycling within hypersaline microbial mats from Guerrero Negro, Baja California Sur, Mexico. Dissolved sulfide within the mats was captured on silver discs and analyzed for its abundance and delta(34)S isotopic composition using high-resolution secondary ion mass spectrometry (nanoSIMS). These results were compared to sulfide and oxygen microelectrode profiles. Two-dimensional microgeochemical mapping revealed well-defined laminations in sulfide concentration (on scales from 1 to 200 microm), trending toward increased sulfide concentrations at depth. Sulfide delta(34)S decreased from approximately +10 per thousand to -20 per thousand in the uppermost 3 mm and oscillated repeatedly between -10 per thousand and -30 per thousand down to a depth of 8 mm. These variations are attributed to spatially variable bacterial sulfate reduction within the mat. A parallel examination of the spatial distribution of known sulfate-reducing bacteria within the family Desulfobacteraceae was conducted using catalyzed reporter deposition fluorescence in situ hybridization. Significant concentrations of Desulfobacteraceae were observed in both oxic and anoxic zones of the mat and occurred in several distinct layers, in large aggregates and heterogeneously dispersed as single cells throughout. The spatial distribution of these microorganisms is consistent with the variation in sulfide concentration and isotopic composition we observed. The parallel application of the methodologies developed here can shed light on micron-scale sulfur cycling within microbially dominated sedimentary environments.

Bone marrow adipose tissue (MAT) accounts for up to 70% of bone marrow volume in healthy adults and increases further in clinical conditions of altered skeletal or metabolic function. Perhaps most strikingly, and in stark contrast to white adipose tissue, MAT has been found to increase during caloric restriction (CR) in humans and many other species. Hypoleptinemia may drive MAT expansion during CR but this has not been demonstrated conclusively. Indeed, MAT formation and function are poorly understood; hence, the physiological and pathological roles of MAT remain elusive. We recently revealed that MAT contributes to hyperadiponectinemia and systemic adaptations to CR. To further these observations, we have now performed CR studies in rabbits to determine whether CR affects adiponectin production by MAT. Moderate or extensive CR decreased bone mass, white adipose tissue mass, and circulating leptin but, surprisingly, did not cause hyperadiponectinemia or MAT expansion. Although this unexpected finding limited our subsequent MAT characterization, it demonstrates that during CR, bone loss can occur independently of MAT expansion; increased MAT may be required for hyperadiponectinemia; and hypoleptinemia is not sufficient for MAT expansion. We further investigated this relationship in mice. In females, CR increased MAT without decreasing circulating leptin, suggesting that hypoleptinemia is also not necessary for MAT expansion. Finally, circulating glucocorticoids increased during CR in mice but not rabbits, suggesting that glucocorticoids might drive MAT expansion during CR. These observations provide insights into the causes and consequences of CR-associated MAT expansion, knowledge with potential relevance to health and disease.

When people are engaged in a skilled behavior, such as occurs in sports, their perceptions relate optical information to their performance. In the present research, we demonstrate the effects of performance on size perception in golfers. We found that golfers who played better judged the hole to be bigger than did golfers who did not play as well. In follow-up laboratory experiments, participants putted on a golf mat from a location near or far from the hole and then judged the size of the hole. Participants who putted from the near location perceived the hole to be bigger than did participants who putted from the far location. Our results demonstrate that perception is influenced by the perceiver's current ability to act effectively in the environment.

OBJECTIVE

HIV infection rates continue to rise among people who inject drugs (PWID) in many lower- and middle-income countries (LMICs). Although progress is being made in prevention and care for PWID in some settings, coverage of essential services remains low. This article reviews the evidence for the benefits of scaling up key interventions as a combination prevention and treatment package for PWID.

RESULTS

WHO defined a comprehensive package of nine interventions for PWID, of which the following four have evidence for effectiveness in reducing HIV incidence: needle and syringe programs (NSP), medication-assisted therapy (MAT), antiretroviral therapy (ART), and HIV counseling and testing (HCT). Coverage of these interventions among PWID in LMICs varies from low (≤20%) to medium (>20-60%). At least a 60% coverage is likely to be required to reduce HIV incidence. Evidence from LMIC contexts suggests that NSP and MAT can reduce high-risk injecting behavior, HCT can reduce risky sexual behavior and ART can plausibly have preventive benefit among PWID for onward parenteral transmission with clearer evidence that antiretroviral therapy (ARV) can prevent onward sexual transmission. Modeling analysis suggests that compared with current low coverage, a scale-up of these four interventions in combination would be a beneficial and cost-effective approach.

CONCLUSIONS

The continuation of significant HIV incidence among PWID in LMIC settings is avoidable with the implementation of immediate scale-up of key harm reduction and ARV treatment interventions. Policymakers should address the structural and resource allocation barriers to allow this scale-up to occur.

Switching of Saccharomyces mating type by replacement of sequences at the MAT locus involves a choice between two donors, HML and HMR. MATalpha cells inhibit recombination along the entire left arm of chromosome III, including HML, whereas MATa cells activate this same region. MATa-dependent activation of HML depends on a small, cis-acting DNA sequence designated the recombination enhancer (RE), located 17 kb centromere-proximal to HML. A comparison of RE sequences interchangeable between Saccharomyces cerevisiae and Saccharomyces carlsbergensis defines a minimum RE of 244 bp. RE activity is repressed in MATalpha cells by binding of the Matalpha2-Mcm1 corepressor to a site within the RE. Mutation of the two Matalpha2 binding sites removes most, but not all, of this repression, and RE chromatin structure in MATalpha cells becomes indistinguishable from that seen in MATa. Surprisingly, a 2-bp mutation in the Mcm1 binding site completely abolishes RE activity in MATa cells; moreover, RE chromatin structure in the MATa mutant becomes very similar to that seen in MATalpha cells with a normal RE, displaying highly ordered nucleosomes despite the absence of Matalpha2. Further, a mutation that alters the ability of Mcm1 to act with Matalpha2 in repressing a-specific genes also alters donor preference in either mating type. Thus, Mcm1 is critically responsible for the activation as well as the Matalpha2-Mcm1-mediated repression of RE activity.

The fungal genus Stemphylium (Ascomycota) contains selfing species that evolved from outcrossing ancestors. To find out how selfing originated, we analyzed the Stemphylium MAT loci that regulate sexual reproduction in ascomycetes and compared MAT structures and phylogeny with a multigene Stemphylium species phylogeny. We found that some Stemphylium species' MAT loci contained a single gene, either MATMATMATMATMAT regions, MATMATMAT regions were able to self. Structural and phylogenetic analyses of the MAT loci showed that the selfing-conferring fused MAT regions were monophyletic with strong support. However, in an organismal phylogeny of Stemphylium species based on 106 isolates and four loci unrelated to mating, selfing arose in two clades, each time with strong support. Isolates with identical fused MAT regions were present in both clades. We showed that a one-time origin of the fused MAT loci, followed by a horizontal transfer across lineages, was compatible with the data. Another group of selfers in Stemphylium only had forward-oriented MATMAT loci, constituting an additional and third origin of selfing in Stemphylium.

Recent advancements in the electrospinning method enable the production of ultrafine solid and continuous fibers with diameters ranging from a few nanometers to a few hundred nanometers with controlled surface and internal molecular structures. A wide range of biodegradable biopolymers can be electrospun into mats with specific fiber arrangement and structural integrity. Through secondary processing, the nanofiber surface can be functionalized to display specific biochemical characteristics. It is hypothesized that the large surface area of nanofibers with specific surface chemistry facilitates attachment of cells and control of their cellular functions. These features of nanofiber mats are morphologically and chemically similar to the extracellular matrix of natural tissue, which is characterized by a wide range of pore diameter distribution, high porosity, effective mechanical properties, and specific biochemical properties. The current emphasis of research is on exploiting such properties and focusing on determining appropriate conditions for electrospinning various polymers and biopolymers for eventual applications including multifunctional membranes, biomedical structural elements (scaffolds used in tissue engineering, wound dressing, drug delivery, artificial organs, vascular grafts), protective shields in specialty fabrics, and filter media for submicron particles in the separation industry. This has resulted in the recent applications for polymer nanofibers in the field of biomedicine and biotechnology.

The earliest reductant for photosynthesis may have been H2. The carbon isotope composition measured in graphite from the 3.8-Ga Isua Supercrustal Belt in Greenland is attributed to H2-driven photosynthesis, rather than to oxygenic photosynthesis as there would have been no evolutionary pressure for oxygenic photosynthesis in the presence of H2. Anoxygenic photosynthesis may also be responsible for the filamentous mats found in the 3.4-Ga Buck Reef Chert in South Africa. Another early reductant was probably H2S. Eventually the supply of H2 in the atmosphere was likely to have been attenuated by the production of CH4 by methanogens, and the supply of H2S was likely to have been restricted to special environments near volcanos. Evaporites, possible stromatolites, and possible microfossils found in the 3.5-Ga Warrawoona Megasequence in Australia are attributed to sulfur-driven photosynthesis. Proteobacteria and protocyanobacteria are assumed to have evolved to use ferrous iron as reductant sometime around 3.0 Ga or earlier. This type of photosynthesis could have produced banded iron formations similar to those produced by oxygenic photosynthesis. Microfossils, stromatolites, and chemical biomarkers in Australia and South Africa show that cyanobacteria containing chlorophyll a and carrying out oxygenic photosynthesis appeared by 2.8 Ga, but the oxygen level in the atmosphere did not begin to increase until about 2.3 Ga.

MAT II, the extrahepatic form of methionine adenosyltransferase (MAT), consists of catalytic alpha(2)/alpha(2') subunits and a noncatalytic beta subunit, believed to have a regulatory function. The full-length cDNA that encodes the beta subunit of human MAT II was cloned and found to encode for a 334-amino acid protein with a calculated molecular weight of 37,552. Analysis of sequence homology showed similarity with bacterial enzymes that catalyze the reduction of TDP-linked sugars. The beta subunit cDNA was cloned into the pQE-30 expression vector, and the recombinant His tagged protein, which was expressed in Escherichia coli, was recognized by antibodies to the human MAT II, to synthetic peptides copying the sequence of native beta subunit protein, and to the rbeta protein. There is no cross-reactivity between the MAT II alpha(2) or beta subunits. None of the anti-beta subunit antibodies reacted with protein extracts of E. coli host cells, suggesting that these bacteria have no beta subunit protein. Interestingly, the rbeta subunit associated with E. coli as well as human MAT alpha subunits. This association changed the kinetic properties of both enzymes and lowered the K(m) of MAT for L-methionine. Together, the data show that we have cloned and expressed the human MAT II beta subunit and confirmed its long suspected regulatory function. This knowledge affords a molecular means by which MAT activity and consequently the levels of AdoMet may be modulated in mammalian cells.

We cloned the pheromone precursor genes of Podospora anserina in order to elucidate their role in the biology of this fungus. The mfp gene encodes a 24-amino-acid polypeptide finished by the CAAX motif, characteristic of fungal lipopeptide pheromone precursors similar to the a-factor precursor of Saccharomyces cerevisiae. The mfm gene encodes a 221-amino-acid polypeptide, which is related to the S. cerevisiae alpha-factor precursor and contains two 13-residue repeats assumed to correspond to the mature pheromone. We deleted the mfp and mfm coding sequence by gene replacement. The mutations specifically affect male fertility, without impairing female fertility and vegetative growth. The male defect is mating type specific: the mat+ Deltamfp and mat- Deltamfm mutants produce male cells inactive in fertilization whereas the mat- Deltamfp and mat+ Deltamfm mutants show normal male fertility. Genetic data indicate that both mfp and mfm are transcribed at a low level in mat+ and mat- vegetative hyphae. Northern-blot analysis shows that their transcription is induced by the mating types in microconidia (mfp by mat+ and mfm by mat-). We managed to cross Deltamfp Deltamfm strains of opposite mating type, by complementation and transient expression of the pheromone precursor gene to trigger fertilization. These crosses were fertile, demonstrating that once fertilization occurs, the pheromone precursor genes are unnecessary for the completion of the sexual cycle. Finally, we show that the constitutively transcribed gpd::mfm and gpd::mfp constructs are repressed at a posttranscriptional level by the noncognate mating type.

Cryptococcus gattii is a primary pathogenic yeast that causes disease in both animals and humans. It is closely related to Cryptococcus neoformans and diverged from a common ancestor approximately 40 million years ago. While C. gattii has a characterized sexual cycle dependent upon a dimorphic region of the genome known as the MAT locus, mating has rarely been observed in this species. In this study, we identify for the first time clinical (both human and veterinary) and environmental isolates from Australia that retain sexual fecundity. A collection of 120 isolates from a variety of geographic locations was analyzed for molecular type, mating type, and the ability to develop mating structures when cocultured with fertile tester strains. Nine isolates produced dikaryotic filaments with paired nuclei, fused clamp connections, and basidiospores. DNA sequence analysis of three genes (URA5, the MATalpha-specific SXI1alpha gene, and the MATa-specific SXI2a gene) revealed little or no variability in URA5 and SXI2a, respectively. However across the 108 MATalpha strains sequenced, the SXI1alpha gene was found to exist as 11 different alleles. Phylogenetic analysis found most variation to occur in the more fertile genotypes. Although some lineages of Australian C. gattii have retained the ability to mate, the majority of isolates were sterile, suggesting that asexuality is the dominant mode of propagation in these populations.

Predictions concerning the consequences of the oceanic uptake of increasing atmospheric carbon dioxide (CO2) have been primarily occupied with the effects of ocean acidification on calcifying organisms, particularly those critical to the formation of habitats (e.g. coral reefs) or their maintenance (e.g. grazing echinoderms). This focus overlooks direct and indirect effects of CO2 on non-calcareous taxa that play critical roles in ecosystem shifts (e.g. competitors). We present the model that future atmospheric [CO2] may act as a resource for mat-forming algae, a diverse and widespread group known to reduce the resilience of kelp forests and coral reefs. We test this hypothesis by combining laboratory and field CO2 experiments and data from 'natural' volcanic CO2 vents. We show that mats have enhanced productivity in experiments and more expansive covers in situ under projected near-future CO2 conditions both in temperate and tropical conditions. The benefits of CO2 are likely to vary among species of producers, potentially leading to shifts in species dominance in a high CO2 world. We explore how ocean acidification combines with other environmental changes across a number of scales, and raise awareness of CO2 as a resource whose change in availability could have wide-ranging community consequences beyond its direct effects.

Photosynthetic microbial mats are remarkably complete self-sustaining ecosystems at the millimeter scale, yet they have substantially affected environmental processes on a planetary scale. These mats may be direct descendents of the most ancient biological communities in which even oxygenic photosynthesis might have developed. Photosynthetic mats are excellent natural laboratories to help us to learn how microbial populations associate to control dynamic biogeochemical gradients.

Candida glabrata, the second most prevalent Candida species colonizing humans, possesses three mating type-like (MTL) loci (MTL1, MTL2, and MTL3). These loci contain pairs of MTL genes with their respective coding regions on complementary Crick and Watson DNA strands. Each pair of genes is separated by a shared intergenic promoter region, the same configuration found at the mating type loci of Saccharomyces cerevisiae. Two of the MTL loci, MTL1 and MTL2, contain either the MTLa1/MTLa2 configuration or the MTLalpha1/MTLalpha2 configuration in different strains. All but one of the 38 tested C. glabrata strains were either aaalpha or aalphaalpha. One test strain was alphaalphaalpha. Based on the mating type genotype, the MTL genes at the MTL1 or MTL2 loci, and the size of the XbaI fragment harboring MTL1 or MTL2, four classes of C. glabrata strains (I, II, III, and IV) were distinguished. Northern analysis revealed that strains were either a-expressors or alpha-expressors and that expression always reflected the genotype of either the MTL1 or MTL2 locus, depending on the class. The expression pattern in each class, therefore, is similar to that observed in S. cerevisiae, which harbors two silent cassette loci, HMR and HML, and the expression locus MAT. High-frequency phenotypic switching between core phenotypes in an alpha-expressing, but not in an a-expressing, strain modulated the level of MTL expression, suggesting a possible relationship between core phenotypic switching and mating.

In previous work we used immunofluorescent staining with specific antibodies to study the distribution of five desmosomal antigens in the epithelia of different vertebrate animals. We showed that all five antigens were present in all epithelia studied in human, bovine, rat, guinea pig, chick and frog (Rana pipiens) tissues. It was concluded that desmosomes are highly conserved structures. This paper extends those studies: by including three other species, a lizard (Lacerta viridis), the axolotl (Ambystoma mexicanum) and the trout (Salmo trutta), and by looking at several tissues in more detail. The principal results are as follows. The epidermis of all species down to the frog stain with equal intensity for all desmosomal antigens. In the epidermis of axolotl and trout, staining for desmosomal plaque constituents is present, but staining for the desmosomal glycoproteins is greatly reduced or absent. Within mammalian species as well as chick, lizard and frog, staining for the 115 X 10(3) and 100 X 10(3) molecular weight desmosomal glycoproteins is less intense in non-epidermal tissues than in the epidermis, while staining for desmosomal plaque constituents and for the 150 X 10(3) molecular weight glycoprotein is undiminished. It is possible, therefore, that slight differences exist between certain glycoproteins of epidermis and non-epidermal epithelia. The hearts of lower vertebrates (lizard, frog, axolotl and trout) stain only for individual desmosomal plaque antigens. The pillar cells of trout gill stain, adjacent to their collagenous columns, for one desmosomal plaque antigen. There is a fibrous cytoplasmic mat in this position but no desmosomes. Thus one of the desmosomal antigens may have a function outside the desmosome.

In this study we determined the composition and biogeochemistry of novel, brightly colored, white and orange microbial mats at the surface of a brine seep at the outer rim of the Chefren mud volcano. These mats were interspersed with one another, but their underlying sediment biogeochemistries differed considerably. Microscopy revealed that the white mats were granules composed of elemental S filaments, similar to those produced by the sulfide-oxidizing epsilonproteobacterium "Candidatus Arcobacter sulfidicus." Fluorescence in situ hybridization indicated that microorganisms targeted by a "Ca. Arcobacter sulfidicus"-specific oligonucleotide probe constituted up to 24% of the total the cells within these mats. Several 16S rRNA gene sequences from organisms closely related to "Ca. Arcobacter sulfidicus" were identified. In contrast, the orange mat consisted mostly of bright orange flakes composed of empty Fe(III) (hydr)oxide-coated microbial sheaths, similar to those produced by the neutrophilic Fe(II)-oxidizing betaproteobacterium Leptothrix ochracea. None of the 16S rRNA gene sequences obtained from these samples were closely related to sequences of known neutrophilic aerobic Fe(II)-oxidizing bacteria. The sediments below both types of mats showed relatively high sulfate reduction rates (300 nmol x cm(-3) x day(-1)) partially fueled by the anaerobic oxidation of methane (10 to 20 nmol x cm(-3) x day(-1)). Free sulfide produced below the white mat was depleted by sulfide oxidation within the mat itself. Below the orange mat free Fe(II) reached the surface layer and was depleted in part by microbial Fe(II) oxidation. Both mats and the sediments underneath them hosted very diverse microbial communities and contained mineral precipitates, most likely due to differences in fluid flow patterns.