Opinions 100, 101 and 102.

The International Committee on Systematics of Prokaryotes has formally made final decisions, taking into account the conclusions of the Judicial Commission, on three pending Requests for an Opinion, thereby allowing the corresponding Opinions to be issued. According to Opinion 100, the request for the recognition of strain A1-86 (=DSM 17629=NCIMB 14373) as the neotype strain of Eubacterium rectale (Hauduroy et al. 1937) Prévot 1938 (Approved Lists 1980) is denied, ruling that a neotype does not need to be designated for E. rectale because strain VPI 0990 (=ATCC 33656=CIP 105953) is considered to be a duplicate isolate of the same strain as VPI 0989 (=ATCC 25578) and may serve as its nomenclatural type. Opinion 101 approves the request that strain ATCC 25946 (=DSM 14877) serves as the type strain of Melittangium lichenicola instead of strain ATCC 25944, formally correcting the Approved Lists of Bacterial Names. Opinion 102 concludes that strain Cc m8 (=DSM 14697=CIP 109128=JCM 12621) is an established neotype strain for the species Myxococcus macrosporus, replacing the designated type strain Windsor M271, and that strain Mx s8 (=DSM 14675=JCM 12634) is an established neotype strain for the species Myxococcus stipitatus, replacing the designated type strain Windsor M78, with some additional considerations about the nature of the type material replaced and about the name Corallococcus (Myxococcus) macrosporus.

Complete Genome Sequence and Comparative Genomics of a Novel Myxobacterium Myxococcus hansupus.

Myxobacteria, a group of Gram-negative aerobes, belong to the class δ-proteobacteria and order Myxococcales. Unlike anaerobic δ-proteobacteria, they exhibit several unusual physiogenomic properties like gliding motility, desiccation-resistant myxospores and large genomes with high coding density. Here we report a 9.5 Mbp complete genome of Myxococcus hansupus that encodes 7,753 proteins. Phylogenomic and genome-genome distance based analysis suggest that Myxococcus hansupus is a novel member of the genus Myxococcus. Comparative genome analysis with other members of the genus Myxococcus was performed to explore their genome diversity. The variation in number of unique proteins observed across different species is suggestive of diversity at the genus level while the overrepresentation of several Pfam families indicates the extent and mode of genome expansion as compared to non-Myxococcales δ-proteobacteria.

Comparative analysis of myxococcus predation on soil bacteria.

Predator-prey relationships among prokaryotes have received little attention but are likely to be important determinants of the composition, structure, and dynamics of microbial communities. Many species of the soil-dwelling myxobacteria are predators of other microbes, but their predation range is poorly characterized. To better understand the predatory capabilities of myxobacteria in nature, we analyzed the predation performance of numerous Myxococcus isolates across 12 diverse species of bacteria. All predator isolates could utilize most potential prey species to effectively fuel colony expansion, although one species hindered predator swarming relative to a control treatment with no growth substrate. Predator strains varied significantly in their relative performance across prey types, but most variation in predatory performance was determined by prey type, with Gram-negative prey species supporting more Myxococcus growth than Gram-positive species. There was evidence for specialized predator performance in some predator-prey combinations. Such specialization may reduce resource competition among sympatric strains in natural habitats. The broad prey range of the Myxococcus genus coupled with its ubiquity in the soil suggests that myxobacteria are likely to have very important ecological and evolutionary effects on many species of soil prokaryotes.

Reclassification of Myxococcus flavescens Yamanaka et al. 1990VP as a later synonym of Myxococcus virescens Thaxter 1892AL.

The taxonomic relatedness between the species Myxococcus flavescens and Myxococcus virescens was investigated. Literature data had already indicated the synonymy between the two species but this observation had not been formalized. Additional evidence that the two taxa represent a single species was provided by comparison of metabolic properties, cellular fatty acid profiles and from a DNA-DNA reassociation value of >80 %. Data from this study led to the proposal that M. flavescens should be reclassified as a later synonym of M. virescens.

New locus important for Myxococcus social motility and development.

The mts locus in salt-tolerant Myxococcus fulvus HW-1 was found to be critical for gliding motility, fruiting-body formation, and sporulation. The homologous genes in Myxococcus xanthus are also important for social motility and fruiting-body development. The mts genes were determined to be involved in cell-cell cohesion in both myxobacterial species.

Adaptation of salt-tolerant Myxococcus strains and their motility systems to the ocean conditions.

More and more studies have indicated that myxobacteria are able to live in seawater conditions, which, however, can decrease the fruiting body formation ability and also the adventurous (A) and social (S) motility systems of the myxobacteria. To learn the adaptation mechanism of the salt-tolerant myxobacteria to marine conditions, we analyzed 10 salt-tolerant Myxococcus strains of their fruiting body formation and motility. The isolates were from marine samples and possessed different levels of salt tolerance. They had the dual motility system and formed fruiting bodies in the presence of suitable seawater concentrations. Some high salt-tolerant strains even lost their fruiting abilities in the absence of seawater. In response to the presence of seawater, the S-motility was found to be increased in the high salt-tolerants but decreased in the low salt-tolerants. The A-motility, on the other hand, was observed in all the salt-tolerant Myxococcus strains, but increased or decreased in response to the presence of seawater. Perceived shifts of fruiting body formation abilities and motilities discovered in the salt-tolerant Myxococcus strains suggested an ecological adaptation of myxobacterial social behaviors to the marine environments.

Byssovorax cruenta gen. nov., sp. nov., nom. rev., a cellulose-degrading myxobacterium: rediscovery of 'Myxococcus cruentus' Thaxter 1897.

A rare, cellulose-decomposing myxobacterium is described, and a new genus name, Byssovorax, is proposed for it. The organism is almost certainly identical to the species 'Myxococcus cruentus' Thaxter 1897, and that species epithet is therefore revived for the novel bacterium: the type strain of Byssovorax cruenta gen. nov., sp. nov., nom. rev. is strain By c2(T) (=DSM 14553(T)=CIP 108850(T)). The G+C content of its DNA is 69.9 mol%. The 16S rRNA gene sequence shows that the species belongs to the family Polyangiaceae, suborder 'Sorangineae', of the Myxococcales. An emended description of the organism is given.

Evolution of an obligate social cheater to a superior cooperator.

Obligate relationships have evolved many times and can be parasitic or mutualistic. Obligate organisms rely on others to survive and thus coevolve with their host or partner. An important but little explored question is whether obligate status is an evolutionarily terminal condition or whether obligate lineages can evolve back to an autonomous lifestyle. The bacterium Myxococcus xanthus survives starvation by the social development of spore-bearing fruiting bodies. Some M. xanthus genotypes defective at fruiting body development in isolation can nonetheless exploit proficient genotypes in chimaeric groups. Here we report an evolutionary transition from obligate dependence on an altruistic host to an autonomous mode of social cooperation. This restoration of social independence was caused by a single mutation of large effect that confers fitness superiority over both ancestral genotypes, including immunity from exploitation by the ancestral cheater. Thus, a temporary state of obligate cheating served as an evolutionary stepping-stone to a novel state of autonomous social dominance.

Microfossils from silicified stromatolitic carbonates of the Upper Proterozoic Limestone-Dolomite 'Series', central East Greenland.

Silicified flake conglomerates and in situ stratiform stromatolites of the Upper Proterozoic (c. 700-800 Ma) Limestone-Dolomite 'Series', central East Greenland, contain well preserved microfossils. Five stratigraphic horizons within the 1200 m succession contain microbial mat assemblages, providing a broad palaeontological representation of late Proterozoic peritidal mat communities. Comparison of assemblages demonstrates that the taxonomy and diversity of mat builder, dweller, and allochthonous populations all vary considerably within and among horizons. The primary mat builder in most assemblages is Siphonophycus inornatum, a sheath-forming prokaryote of probable but not unequivocally established cyanobacterial affinities. An unusual low diversity unit in Bed 17 is dominated by a different builder, Tenuofilum septatum, while a thin cryptalgal horizon in Bed 18 is built almost exclusively by Siphonophycus kestron. Although variable taphonomic histories contribute to observed assemblage variation, most differences within and among horizons appear to reflect the differential success or failure of individual microbial populations in colonizing different tidal flat microenvironments. Twenty-two taxa are recognized, of which two are described as new: Myxococcoides stragulescens n.sp. and Scissilisphaera gradata n. sp.