The Interactions of Vibrio vulnificus and the Oyster Crassostrea virginica

The human bacterial pathogen, Vibrio vulnificus, is found in brackish waters and is concentrated by filter-feeding molluscan shellfish, especially oysters, which inhabit those waters. Ingestion of raw or undercooked oysters containing virulent strains of V. vulnificus can result in rapid septicemia and death in 50 % of victims. This review summarizes the current knowledge of the environmental interactions between these two organisms, including the effects of salinity and temperature on colonization, uptake, and depuration rates of various phenotypes and genotypes of the bacterium, and host–microbe immunological interactions.     

Identification of a Residue Affecting Fatty Alcohol Selectivity in Wax Ester Synthase

The terminal enzyme in the bacterial wax ester biosynthetic pathway is the bifunctional wax ester synthase/acyl-coenzyme A:diacylglycerol acyltransferase (WS/DGAT), which utilizes a fatty alcohol and a fatty acyl-coenzyme A (CoA) to synthesize the corresponding wax ester. In this report, we identify a specific residue in WS/DGAT enzymes obtained from Marinobacter aquaeolei VT8 and Acinetobacter baylyi that alters fatty alcohol selectivity and kinetic parameters when modified to alternative residues.     

Increases in the Amounts of Vibrio spp. in Oysters upon Addition of Exogenous Bacteria

The bacterial pathogen Vibrio vulnificus is found naturally in brackish coastal waters but can be greatly concentrated by filter-feeding organisms such as shellfish. Numerous experiments in which exogenous V. vulnificus cells are added to oysters in an attempt to measure uptake and depuration have been performed. In nearly all cases, results have shown that laboratory-grown bacteria are rapidly taken up by the oysters but ultimately eliminated, while naturally present Vibrio populations in oysters are resistant to depuration. In this study, oysters harvested during winter months, with low culturable Vibrio concentrations, were incubated in aquaria supplemented with strains of V. vulnificus that were either genotypically or phenotypically distinct from the background bacteria. These exogenous cells were eliminated from the oysters, as previously seen, but other vibrios already inhabiting the oysters responded to the V. vulnificus inoculum by rapidly increasing in number and maintaining a large stable population. The presence of such an oyster-adapted Vibrio population would be expected to prevent colonization by exogenous V. vulnificus cells, thus explaining the rapid depuration of these added bacteria.     

Airborne pollen of Brisbane,Australia: A five-year record, 1994 - 1999

The seasonal incidence of pollen in the atmosphere of Brisbane has been established from a near-continuous, volumetric trapping program over the five-year period, July 1994-June 1999. Grass pollen accounts for 71.6% of the average annual pollen load with highest densities (up to 150 grains/m 3 ) recorded in summer and autumn. Significant contributions were also made by taxa of the Cupressaceae (8.7%) and Urticaceae (1.8%) during spring and of the Pinaceae (4.5%) during winter. Pollen seasons of the Casuarinaceae (6.5%) and Myrtaceae (3.2%) are more extended, the former peaking in late winter and the latter in late spring. The onset and duration of the Poaceae and Urticaceae seasons varied from year to year, being later when precipitation levels were low in the late spring-early summer months. Total pollen numbers and grass pollen densities are substantially less than those recorded from southern Australia. Nevertheless, respiratory disease in Brisbane affects up to 10% of the population, and airborne pollen of Poaceae, Urticaceae, Cupressaceae, Pinaceae, and Myrtaceae have been implicated in the release of allergens.     

Discovery of a new HIV-1 inhibitor scaffold and synthesis of potential prodrugs of indazoles

A new oxazole scaffold showing great promise in HIV-1 inhibition has been discovered by cell-based screening of an in-house library and scaffold modification. Follow-up SAR study focusing on the 5-aryl substituent of the oxazole core has identified 4k (EC₅₀ = 0.42 μM, TI = 50) as a potent inhibitor. However, the analogues suffered from poor aqueous solubility. To address this issue, we have developed broadly applicable potential prodrugs of indazoles. Among them, N-acyloxymethyl analogue 11b displayed promising results (i.e., increased aqueous solubility and susceptibility to enzymatic hydrolysis). Further studies are warranted to fully evaluate the analogues as the potential prodrugs with improved physiochemical and PK properties     

Microbial diversity and diazotrophy associated with the freshwater non-heterocyst forming cyanobacterium Lyngbya robusta

Lake Atitlan, Guatemala, a freshwater lake in South America, experiences annually recurring blooms comprised of the planktic filamentous cyanobacterium Lyngbya robusta. Previous physiochemical characterisation of the bloom identified diurnal nitrogenase activity typical of non-heterocystous cyanobacteria, in addition to the low-level detection of the cyanotoxins cylindrospermopsin and saxitoxin. A molecular approach, combining deep sequencing of the 16S rRNA and nifH genes, was applied to a cyanobacteria-dominated sample collected during the extensive 2009 bloom. Lyngbya accounted for over 60 % of the total 16S rRNA sequences with the only other cyanobacterial species detected being the picophytoplankton Synechococcus. The remaining bacterial population was comprised of organisms typical of other eutrophic freshwater bodies, although the proportionate abundances were atypical. An obligate anaerobe Opitutus, not typically found in freshwater systems, was identified within the community which suggests it may have a role in enhancing nitrogen fixation. Primary nitrogen fixation was attributed to Lyngbya, with other putative nitrogen fixers, Desulfovibrio, Clostridium and Methylomonas, present at very low abundance.     

Deep sequencing of non-ribosomal peptide synthetases and polyketide synthases from the microbiomes of Australian marine sponges

The biosynthesis of non-ribosomal peptide and polyketide natural products is facilitated by multimodular enzymes that contain domains responsible for the sequential condensation of amino and carboxylic subunits. These conserved domains provide molecular targets for the discovery of natural products from microbial metagenomes. This study demonstrates the application of tag-encoded FLX amplicon pyrosequencing (TEFAP) targeting non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) genes as a method for determining the identity and diversity of natural product biosynthesis genes. To validate this approach, we assessed the diversity of NRPS and PKS genes within the microbiomes of six Australian marine sponge species using both TEFAP and metagenomic whole-genome shotgun sequencing approaches. The TEFAP approach identified 100 novel ketosynthase (KS) domain sequences and 400 novel condensation domain sequences within the microbiomes of the six sponges. The diversity of KS domains within the microbiome of a single sponge species Scopalina sp. exceeded that of any previously surveyed marine sponge. Furthermore, this study represented the first to target the condensation domain from NRPS biosynthesis and resulted in the identification of a novel condensation domain lineage. This study highlights the untapped potential of Australian marine sponges for the isolation of novel bioactive natural products. Furthermore, this study demonstrates that TEFAP approaches can be applied to functional genes, involved in natural product biosynthesis, as a tool to aid natural product discovery. It is envisaged that this approach will be used across multiple environments, offering an insight into the biological processes that influence the production of secondary metabolites.