Multicellular behavior in bacteria: communication, cooperation, competition and cheating.

The sociobiology of bacteria, largely unappreciated and ignored by the microbiology research community two decades ago is now a major research area, catalyzed to a significant degree by studies of communication and cooperative behavior among the myxobacteria and in quorum sensing (QS) and biofilm formation by pseudomonads and other microbes. Recently, the topic of multicellular cooperative behaviors among bacteria has been increasingly considered in the context of evolutionary biology. Here we discuss the significance of two recent studies of the phenomenon of "cheating" mutants and their exploitation of cooperating microbial populations of Pseudomonas aeruginosa.

Sergei Winogradsky: a founder of modern microbiology and the first microbial ecologist.

Sergei Winogradsky, was born in Russia in 1856 and was to become a founder of modern microbiology. After his Master's degree work on the nutrition and growth physiology of the yeast Mycoderma vini at the University of St. Petersburg, he joined the laboratory of Anton DeBary in Strassburg. There he carried out his studies on the sulfur-oxidizing bacterium Beggiatoa which resulted in his formulation of the theory of chemolithotrophy. He then joined the Swiss Polytechnic Institute in Zurich where he did his monumental work on bacterial nitrification. He isolated the first pure cultures of the nitrifying bacteria and confirmed that they carried out the separate steps of the conversion of ammonia to nitrite and of nitrite to nitrate. This led directly to the concept of the cycles of sulfur and nitrogen in Nature. He returned to Russia and there was the first to isolate a free-living dinitrogen-fixing bacterium. In the flush of success, he retired from science and spent 15 years on his familial estate in the Ukraine. The Russian revolution forced him to flee Russia. He joined the Pasteur Institute in Paris where he spent his remaining 24 years initiating and developing the field of microbial ecology. He died in 1953.

Pheromone-inducible conjugation in Enterococcus faecalis: a model for the evolution of biological complexity?

Pheromone-inducible transfer of the plasmid pCF10 in Enterococcus faecalis is regulated using a complicated network of proteins and RNAs. The plasmid itself has been assembled from parts garnered from a variety of sources, and many aspects of the system resemble a biological kluge. Recently several new functions of various pCF10 gene products that participate in regulation of plasmid transfer have been identified. The results indicate that selective pressures controlling the evolution of the plasmid have produced a highly complex regulatory network with multiple biological functions that may serve well as a model for the evolution of biological complexity.

A mutation that affects fibril protein, development, cohesion and gene expression in Myxococcus xanthus.

Extracellular matrix fibrils are involved in the cell-cell interactions of the social prokaryote, Myxococcus xanthus. The fibrils are composed of a carbohydrate backbone and a set of five integral fibrillar proteins (IFPs) ranging from 14 to 66 kDa. As part of an attempt to understand the function(s) of the IFPs, a mutant (ifp-1:20) was generated that lacks IFP-1:20, one of the fibril proteins, as shown by Western blot analysis of both whole cells and isolated fibrils. Unlike those of the parent strain, the fibrils of the mutant were removed easily from the cells by shear forces. Development in ifp-1:20 was aberrant--aggregation and early mound formation were delayed by 6-10 h and mature fruiting bodies never formed. Myxospore production was also greatly reduced. Additionally, fibril-mediated cohesion in ifp-1:20 was changed. Cohesion resulted in chains of cells rather than the characteristic clumps of cells seen for the parent strain. Isolated ifp-1:20 fibrils, unlike wild-type fibrils, could not rescue cohesion of non-cohesive, fibril-negative dsp cells, supporting the notion that the fibrils were functionally altered. The mutation also reduced developmental gene expression by three- to fourfold in omega 4521, a transposon insertion mutant expressed early in development. Expression of a later developmental gene fusion was not affected, suggesting that the fibrils may not be required for later developmental gene expression. These data suggest that intact fibrils may function early in development to facilitate close cell proximity for signal exchange.

Isolation and characterization of novel marine-derived actinomycete taxa rich in bioactive metabolites.

A unique selective enrichment procedure has resulted in the isolation and identification of two new genera of marine-derived actinobacteria. Approximately 90% of the microorganisms cultured by using the presented method were from the prospective new genera, a result indicative of its high selectivity. In this study, 102 actinomycetes were isolated from subtidal marine sediments collected from the Bismarck Sea and the Solomon Sea off the coast of Papua New Guinea. A combination of physiological parameters, chemotaxonomic characteristics, distinguishing 16S rRNA gene sequences, and phylogenetic analysis based on 16S rRNA genes provided strong evidence for the two new genera (represented by strains of the PNG1 clade and strain UMM518) within the family Micromonosporaceae. Biological activity testing of fermentation products from the new marine-derived actinomycetes revealed that several had activities against multidrug-resistant gram-positive pathogens, malignant cells, and vaccinia virus replication.