Pentacyclic triterpenoids of the hopane family were found in about half of some 100 strains of prokaryotes belonging to diverse taxonomic groups, such a wide distribution indicating the biological significance of these compounds Hopanoids were found in almost all the cyanobacteria and obligate methylotrophs examined, in all the purple non-sulphur bacteria studied and in many taxonomically diverse Gram-negative or Gram-positive chemohetero-trophs They were absent in all archaebacteria and purple sulphur bacteria examined as well as in various other Gram-positive or Gram-negative genera The C30 hopanoids, diploptene and diplopterol, are present in almost all hopanoid-containing prokaryotes The major compounds are always the C35 bacteriohopanepolyols, which are present at a level of 01-2 mg per g dry weight, the most common one being bacteriohopanetetrol Because of their structural characteristics and their influence on the properties of biological membrane models, these compounds might be the structural equivalents of the sterols found in eukaryotes

Distribution of Hopanoid Triterpenes in Prokaryotes

The metabolic capacity for nitrogen fixation is known to be present in several prokaryotic species scattered across taxonomic groups. Experimental detection of nitrogen fixation in microbes requires species-specific conditions, making it difficult to obtain a comprehensive census of this trait. The recent and rapid increase in the availability of microbial genome sequences affords novel opportunities to re-examine the occurrence and distribution of nitrogen fixation genes. The current practice for computational prediction of nitrogen fixation is to use the presence of the nifH and/or nifD genes. Based on a careful comparison of the repertoire of nitrogen fixation genes in known diazotroph species we propose a new criterion for computational prediction of nitrogen fixation: the presence of a minimum set of six genes coding for structural and biosynthetic components, namely NifHDK and NifENB. Using this criterion, we conducted a comprehensive search in fully sequenced genomes and identified 149 diazotrophic species, including 82 known diazotrophs and 67 species not known to fix nitrogen. The taxonomic distribution of nitrogen fixation in Archaea was limited to the Euryarchaeota phylum; within the Bacteria domain we predict that nitrogen fixation occurs in 13 different phyla. Of these, seven phyla had not hitherto been known to contain species capable of nitrogen fixation. Our analyses also identified protein sequences that are similar to nitrogenase in organisms that do not meet the minimum-gene-set criteria. The existence of nitrogenase-like proteins lacking conserved co-factor ligands in both diazotrophs and non-diazotrophs suggests their potential for performing other, as yet unidentified, metabolic functions. Our predictions expand the known phylogenetic diversity of nitrogen fixation, and suggest that this trait may be much more common in nature than it is currently thought. The diverse phylogenetic distribution of nitrogenase-like proteins indicates potential new roles for anciently duplicated and divergent members of this group of enzymes.

/pdf/distribution-of-nitrogen-fixation-and-nitrogenase-like-19ylssm4l2.pdf

Distribution of nitrogen fixation and nitrogenase-like sequences amongst microbial genomes

The caulobacters: ubiquitous unusual bacteria.

Summary: Caulobacter crescentus is an aquatic Gram-negative alphaproteobacterium that undergoes multiple changes in cell shape, organelle production, subcellular distribution of proteins, and intracellular signaling throughout its life cycle. Over 40 years of research has been dedicated to this organism and its developmental life cycles. Here we review a portion of many developmental processes, with particular emphasis on how multiple processes are integrated and coordinated both spatially and temporally. While much has been discovered about Caulobacter crescentus development, areas of potential future research are also highlighted.

Getting in the Loop: Regulation of Development in Caulobacter crescentus

When we use direct microscopic techniques to examine bacteria growing in natural and pathogenic ecosystems, we are forcibly struck by the profound differences between these organisms and cells within derived in vitro laboratory cultures. The development of a series of new techniques for the stabilization and visualization of bacterial surface structures has intensified these differences because, as we come to understand bacterial surface structures more fully, we see that they comprise a very complex and fluid interface with the environment which the bacterium must maintain in order to survive amid the ubiquitous antibacterial agents and factors in nature.

Phenomena of Bacterial Adhesion

Morphogenesis and differentiation in Rhodomicrobium vannielii and other budding and prosthecate bacteria.

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Morphogenesis and differentiation in Rhodomicrobium vannielii and other budding and prosthecate bacteria.