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Two myxobacterial strains (KH5-1 T and NO1) were isolated from the activated sludge tanks treating municipal sewage wastewater in Japan. These strains were recognised as myxobacteria based on their phenotypic characteristics of swarming colonies and fruiting bodies. Phylogenetic analyses using the 16S rRNA gene revealed that strains KH5-1 T and NO1 were affiliated with the genus Corallococcus, with the closest neighbours being Corallococcus exercitus AB043A T (99.77% and 99.84%, respectively). Genome comparisons using orthologous average nucleotide identity (orthoANI) and digital DNA-DNA hybridisation similarity (dDDH) with strains KH5-1 T and NO1 and their phylogenetically close relatives in Corallococcus spp. were below the thresholds. The major cellular fatty acids of strains KH5-1 T and NO1 were iso-C 15:0 (31.9%, 30.0%), summed feature 3 (comprising C 16:1 ω7c and/or C 1 6:1 ω6c) (20.2%, 17.7%), and iso-C 17:0 (12.1%, 14.8%), and the major respiratory quinone was found to be menaquinone (MK)-8. Based on the phenotypic, chemotaxonomic, and phylogenetic evidence, strains KH5-1 T and NO1 represent a new species in the genus Corallococcus, for which the proposed name is Corallococcus caeni sp. nov. The type strain is KH5-1 T (= NCIMB 15510 T  = JCM 36609 T )., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

An expanded neighbour-joining tree of myxobacteria is presented based on the analysis of 16S rRNA gene sequences of 101 strains (including types) representing 3 suborders, 6 families, 20 genera, 46 species, and 12 other novel taxa. The distinctions amongst members of the three suborders (Sorangiineae, Cytobacterineae and Nannocystineae) are reaffirmed. The positions of anaerobic myxobacteria, novel groups (Pyxidicoccus and several Cystobacter species) in Cystobacterineae, the marine genera (Plesiocystis, Haliangium, Enhygromyxa), and two additional novel taxa ('Paraliomyxa miuraensis', brackish-water isolate) were together revealed for the first time. Changes in the nomenclature of several isolates (Polyangium vitellinum Pl vt1(T), Polyangium thaxteri Pl t3, Polyangium cellulosum, NOSO-1, NOCB-2, NOCB-4) are also highlighted. Suborders Sorangiineae and Nannocystineae hold great promise for novel strain discovery. In Sorangiineae, the new family Phaselicystidaceae, with a monotypic genus, was added. Nine additional novel taxa were discovered in this suborder for which new genera or even families may be erected in the near future. These taxa appear to represent the so-called viable but not culturable (VBNC) group of myxobacteria. Based on at least 4% phylogenetic distance, new clades were formed comprising of novel Nannocystineae and Sorangiineae isolates. Overall, the myxobacteria, on the basis of bracket distance, could be divided into 16 clusters, as supported by tree topology and a morphology-based approach., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The diversity of 16S-23S rDNA intergenic spacer regions (ISR) among cellulolytic myxobacterial strains was assayed. Agarose gel electrophoresis of PCR amplification products from ten strains shows that there are at least four copies of rRNA operons in the genus Sorangium, based on their size and restriction enzymatic digest maps. There are two sequence organization patterns: tRNA(Ile)-tRNA(Ala)-containing ISR and tRNA-lacking ISR. The tRNA-containing ISRs are highly similar among strains and within a strain (more than 98% similarity) and contain the essential functional regions, such as a ribonuclease III recognition site and an antiterminator recognition site boxA. The tRNA-lacking ISR has no such functional sites that are important for yielding mature rRNA, which suggests that this type of rRNA operons might be degenerate. The tRNA-lacking ISR is divided into two types based on their sizes and sequences, which exhibits about 90% similarity within each type. Thus, the tRNA-lacking ISR polymorphisms can be used to discriminate among different strains of sorangial species.

Myxobacteria are soil bacteria whose unusually social behavior distinguishes them from other groups of procaryotes. Perhaps the most remarkable aspect of their social behavior occurs during development, when tens of thousands of cells aggregate and form a colorful fruiting body. Inside the fruiting body the vegetative cells convert into dormant, resistant myxospores. However, myxobacterial social behavior is not restricted to the developmental cycle, and three other social behaviors have been described. Vegetative cells have a multigene social motility system in which cell-cell contact is essential for gliding in multicellular swarms. Cell growth on protein is cooperative in that the growth rate increases with the cell density. Rippling is a periodic behavior in which the cells align themselves in ridges and move in waves. These social behaviors indicate that myxobacterial colonies are not merely collections of individual cells but are societies in which cell behavior is synchronized by cell-cell interactions. The molecular basis of these social behaviors is becoming clear through the use of a combination of behavioral, biochemical, and genetic experimental approaches.

The molar percentages of guanine plus cytosine in the DNA of 51 strains of Simonsiellaceae were determined by buoyant density ultracentrifugation of cell lysates in CsCl. The DNA base ratios ranged from 41-55 mole-% guanine plus cytosine. These values fall within the range known for the Order Cytophagales, the non-fruiting gliding bacteria, and are outside the range of the Order Myxobacterales, the fruiting myxobacteria. Among the strains of the genus Simonsiella, four distinct group can be delineated on the basis of source of origin (sheep, dog, cat, human) and GC content. The neotype of Alysiella filiformis has a GC content of 45.4 mole-%.