The Caenorhabditis elegans spe-49 gene is required for fertilization and encodes a sperm-specific transmembrane protein homologous to SPE-42.

Fertilization, the fusion of sperm and oocyte to form a zygote, is the first and arguably the most important cell-cell interaction event in an organism's life. Forward and reverse genetic approaches in the nematode Caenorhabditis elegans have identified many genes that are required for gametogenesis and fertilization and thus are beginning to elucidate the molecular pathways that underlie these processes. We identified an allele of the spe-49 gene in a second filial generation (F2 ) mutagenesis screen for spermatogenesis-defective (spe) mutants. Mutant worms for spe-49 produce sperm that have normal morphology, activate to form ameboid spermatozoa, and can migrate to and maintain their position in the hermaphrodite reproductive tract but fail to fertilize oocytes. This phenotype puts spe-49 in the spe-9 class of late-acting genes that function in sperm at the time of fertilization. We cloned the spe-49 gene through a combination of deficiency mapping, transgenic rescue, and genomic sequencing. spe-49 messenger RNA (mRNA) is enriched in male germ cells, and the complementary DNA (cDNA) encodes a predicted 772-amino-acid six-pass transmembrane protein that is homologous to SPE-42. Indeed, SPE-49 and SPE-42 have identical predicted membrane topology and domain structure, including a large extracellular domain with six conserved cysteine residues, a DC-STAMP domain, and a C-terminal cytoplasmic domain containing a C4-C4 RING finger motif. The presence of two SPE-42 homologs in animal genomes from worms to humans suggests that these proteins are highly conserved components of the molecular apparatus required for the sperm-oocyte recognition, binding, and fusion.

Selection and molecular characterization of cellulolytic-xylanolytic fungi from surface soil-biomass mixtures from Black Belt sites.

Plant biomass is an abundant renewable natural resource that can be transformed into chemical feedstocks. Enzymes used in saccharification of lignocellulosic biomass are a major part of biofuel production costs. A cocktail of cellulolytic and xylanolytic enzymes are required for optimal saccharification of biomass. Accordingly, thirty-two fungal pure cultures were obtained from surface soil-biomass mixtures collected from Black Belt sites in Alabama by culturing on lignocellulosic biomass medium. The fungal strains were screened for the coproduction of cellulolytic and xylanolytic enzymes. Strains that displayed promising levels of cellulolytic and xylanolytic enzymes were characterized by molecular analysis of DNA sequences from the large subunit and internal transcribed spacer (ITS) of their ribosomal RNA gene. Nucleotide sequence analysis revealed that two most promising isolates FS22A and FS5A were most similar to Penicillium janthinellum and Trichoderma virens. Production dynamics of cellulolytic and xylanolytic enzymes from these two strains were explored in submerged fermentation. Volumetric productivity after 120 h incubation was 121.08 units/L/h and 348 units/L/h for the filter paper cellulase and xylanase of strain FS22A, and 90.83 units/L/h and 359 units/L/h, respectively for strain FS5A. Assays with 10 times dilution of enzymes revealed that the activities were much higher than that observed in the crude culture supernatant. Additionally, both FS22A and FS5A also produced amylase in lignocellulose medium. The enzyme profiles of these strains and their activities suggest potential applications in cost effective biomass conversion and biodegradation.

Sapling growth and survivorship as affected by light and flooding in a river floodplain forest of southeast Texas.

We investigated the effects of light and flooding on growth and survivorship of saplings in a river floodplain forest of southeast Texas. Growth responses to light were consistent with the expectation that shade-intolerant species grow faster than shade-tolerant species in high light, and vice versa. Mortality risk was not associated with shade tolerance level unless high mortality risks associated with a period of high flooding were removed. These results support the hypothesis that shade-tolerant species in floodplains may be limited by flooding as previous studies suggested. Also, compared to their performance at a nearby mesic site, common species showed little intraspecific difference in shade tolerance, especially for shade-intolerant species. Finally, the positive correlation between low-light growth and survivorship suggests that carbon allocation to continued growth may be favored as a sapling strategy in floodplains.

Sapling growth and survivorship as a function of light in a mesic forest of southeast Texas, USA.

For seven species in a mature mesic forest in southeast Texas, we estimated species-specific parameters representing radial growth in high light and low light for tree saplings. Shade-intolerant species had higher asymptotic growth rates and lower low-light growth than tolerant species. Inspection of species positions on graphs of low-light growth versus high-light growth suggested that there was a trade-off between these two processes across species. By linking functions of growth versus light and mortality versus growth, we also found that shade-intolerant species had higher mortality risk at low light and stronger sensitivity of mortality to light than shade-tolerant species. Moreover, we found that low-light survival and high-light growth were negatively correlated across species. In contrast to northern hardwood forests, where sapling survival in low light may be achieved at the expense of growth, our results suggested that shade-tolerant species in this southern mixed forest can grow faster as well as survive better than shade-intolerant species in low light. We conclude that both sapling growth and survival are important components of shade tolerance and their relationships may be system-specific.

The incidence of group B streptococcus in the vaginal tracts of pregnant women in central Alabama.

Group B streptococcus (Streptococcus agalactiae) or GBS is the most common cause of neonatal sepsis and meningitis in the United States. One important risk factor for infants who acquire GBS is maternal colonization. Colonization rates have been estimated in various studies to be between 15% and 35% of pregnant women. Colonization rates for black women have also been shown to be higher than for non-blacks. Local data were collected and compared to those of other studies. Of the pregnant women in this study overall, 22.76% tested positive for GBS. Black women were colonized by GBS (35.71%) significantly more often than non-black women (19.84%; G = 8.9729, p < 0.00274). Generalized linear models were used to examine age and race. Both maternal age and the interaction of maternal race and age as predictors of infection were ruled out, leaving only race as a significant predictor of colonization.