Induction of Larval Metamorphosis of the Coral Acropora millepora by Tetrabromopyrrole Isolated from a Pseudoalteromonas Bacterium

The induction of larval attachment and metamorphosis of benthic marine invertebrates is widely considered to rely on habitat specific cues. While microbial biofilms on marine hard substrates have received considerable attention as specific signals for a wide and phylogenetically diverse array of marine invertebrates, the presumed chemical settlement signals produced by the bacteria have to date not been characterized. Here we isolated and fully characterized the first chemical signal from bacteria that induced larval metamorphosis of acroporid coral larvae (Acropora millepora). The metamorphic cue was identified as tetrabromopyrrole (TBP) in four bacterial Pseudoalteromonas strains among a culture library of 225 isolates obtained from the crustose coralline algae Neogoniolithon fosliei and Hydrolithon onkodes. Coral planulae transformed into fully developed polyps within 6 h, but only a small proportion of these polyps attached to the substratum. The biofilm cell density of the four bacterial strains had no influence on the ratio of attached vs. non-attached polyps. Larval bioassays with ethanolic extracts of the bacterial isolates, as well as synthetic TBP resulted in consistent responses of coral planulae to various doses of TBP. The lowest bacterial density of one of the Pseudoalteromonas strains which induced metamorphosis was 7,000 cells mm−2 in laboratory assays, which is on the order of 0.1 –1% of the total numbers of bacteria typically found on such surfaces. These results, in which an actual cue from bacteria has been characterized for the first time, contribute significantly towards understanding the complex process of acroporid coral larval settlement mediated through epibiotic microbial biofilms on crustose coralline algae

A Summary of Recent Microbial Discoveries in Biological Nutrient Removal from Wastewater

A number of recent studies has focussed on discovering the microorganisms responsible for various nutrient removal processes in the wastewater treatment industry. This is despite the fact that many wastewater personnel would think that these microorganisms were already known. The sample dilution and plating methods, previously the major ones used by microbiologists, have lead to the isolation of various microorganisms with specific phenotypes of interest. Consequently, Nitrosomonas and Nitrobacter have been described as the major ammonia and nitrite oxidisers, respectively. Acinetobacter has been attributed with the enhanced biological phosphorus removal (EBPR) phenotype due to its predominance in isolations from EBPR plants. However, the true situation is not so clear and even worse, the above organisms may not even play any role in the transformations for which they have achieved such acclaim. The introduction of methods that allow microbiologists to investigate the microbial composition in mixed cultures has begun to resolve the questions on the true identity of microorganisms responsible for nutrient transformations. These methods also allow the ready in situ confirmation of such hypotheses on organism identity and allow this to be linked with organism phenotype. To answer the question on organism identity, enrichment culture around specific phenotypes can still be employed, however, instead of the enrichment of one microorganism over all others, a consortium is obtained. The enriched consortium is investigated by in situ identification methods like fluorescence in situ hybridisation (FISH) with domain, division, and sub-division level probes. A fairly clear picture of the "global" microbial community structure is thus obtained. Evolutionarily conserved genes like those for the 16S rRNA are extracted from the enriched culture and analysed to place them in the phylogenetic tree. Sequences from groups known to dominate the enrichment culture from FISH, can be focussed upon and more intensively studied, including the design of novel probes for FISH on the enrichment culture. The same approach using FISH and analysis of conserved genes from full-scale operations has also been employed to identify the organisms of relevance to specific nutrient transformations. The final product is a suite of FISH probes that can be used with any mixed culture biomass for enumeration of organisms of interest and correlation of their abundance with process performance. Once the identity of the organisms truly responsible for nutrient transformations is known, their physiological parameters can be studied

Whole cell probing with fluorescently labelled probes for in situ analysis of microbial populations

Abstract not available

Microbial Population Dynamics in Biological Wastewater Treatment - Selected Papers from the 4th IWA Activated Sludge Population Dynamics Conference (ASPD4), held in Surfers Paradise, Queensland, Australia, 17-20 July 2005 - Preface

Abstract not available

The mechanism of stabilization of actinomycete foams and the prevention of foaming under laboratory conditions

Cultures of Nocardia amarae give rise to cell-stabilized foams in a laboratory scale foaming apparatus. The organism produces a surfactant and the cells are very hydrophobic; factors which, in terms of froth flotation theory, are essential for foam production and transport of the cells from the aqueous to the bubble phase. The addition of montmorillonitic clay to the culture prior to foaming prevents foam stabilization. The results obtained suggest the formation of a salt-dependent, reversible, bacterium-montmorillonite complex which prevents transport of cells to the bubble phase