New Lineage of Filamentous, Spore-Forming, Gram-Positive Bacteria from Soil

Abstract

A novel bacterial strain that was isolated from an Italian soil and was designated SOSP1-21 T forms branched mycelia in solid and liquid media and has a filamentous morphology similar to that of some genera belonging to the Actinobacteria. Electron microscopy showed that this organism has a grape-like appearance, resulting from interlacing of spores originating from sporophoric hyphae. Ten strains that are morphologically related to SOSP1-21 T were recovered from soil. Phylogenetic analyses of 16S rRNA gene segments confirmed the relatedness of these strains to SOSP1-21 T and indicated that the newly isolated strains form separate clades in a deeply branching lineage. The closest matches for the 16S rRNA sequences of all the strains (around 79% identity) were matches with representatives of the Chloroflexi, although the affiliation with this division was not supported by high bootstrap values. The strains are mesophilic aerobic heterotrophs and are also capable of growing under microaerophilic conditions. They all stain gram positive. Strain SOSP1-21 T contains ornithine, alanine, glutamic acid, serine, and glycine as the peptidoglycan amino acids. In addition, an unusual level of C16:1 2OH (30%) was found in the cellular fatty acids. The G؉C content of SOSP1-21 T genomic DNA is 53.9%, and MK-9(H 2 ) was the only menaquinone detected. All these data suggest that SOSP1-21T and the related strains may constitute a new division of filamentous, spore-forming, gram-positive bacteria. We propose the name Ktedobacter racemifer gen. nov., sp. nov. for strain SOSP1-21 T .

Cultivation of Uncultured Chloroflexi Subphyla: Significance and Ecophysiology of Formerly Uncultured Chloroflexi 'Subphylum I' with Natural and Biotechnological Relevance

“…Recently, a novel strain was isolated from a soil and named Ktedobacter racemifer (11). The bacterium is a Gram-positive, aerobic, chemolithoorganoheterotrophic organism that produces branched vegetative mycelia, growing well under microaerobic conditions; this finding further expanded the morphological diversity of the phylum.…”

“…The bacterium is a Gram-positive, aerobic, chemolithoorganoheterotrophic organism that produces branched vegetative mycelia, growing well under microaerobic conditions; this finding further expanded the morphological diversity of the phylum. Phylogenetically, the bacterium represents a new subphylum-level clade of the Chloroflexi phylum, to which the name Ktedonobacteria classis nov. has been given (11,23). The subphylum (class)-level clade contains a variety of environmental gene clones (>100 sequences in public databases) retrieved mainly from soil samples (these sequences can be browsed on the recent version of the greengene database (http://greengenes.lbl.gov/).…”

Thermosporothrix narukonensis sp. nov., belonging to the class Ktedonobacteria, isolated from fallen leaves on geothermal soil, and emended description of the genus Thermosporothrix

“…The class Ktedonobacteria was first proposed by Cavaletti et al (2006) and later placed in the phylum Chloroflexi (Yabe et al, 2011). The class currently consists of only five species: Ktedonobacter racemifer (Cavaletti et al, 2006) and Thermosporothrix hazakensis (Yabe et al, 2010a) belonging to the order Ktedonobacterales, and Thermogemmatispora onikobensis (Yabe et al, 2011), Thermogemmatispora foliorum (Yabe et al, 2011) and Thermogemmatispora carboxidivorans (King & King, 2014) belonging to the order Thermogemmatisporales.…”

Temperature responses of carbon monoxide and hydrogen uptake by vegetated and unvegetated volcanic cinders

“…These sequences, which are most closely related to a class of bacteria consisting of a majority of thermophiles, have not been observed in Canopy site coxL or 16S rRNA gene sequence libraries. Thus, one could anticipate an adaptive response to elevated temperature for Bare cinder CO uptake even though some Ktedonobacteria are mesophilic (Cavaletti et al, 2006).…”

“…Previous molecular ecological analyses have also shown that Bare cinder CO oxidizer communities consist primarily of taxa most closely related to Ktedonobacteria (Weber and King, 2010), a group of largely thermophilic or thermotolerant strains isolated from hot compost and geothermally-heated soils (Cavaletti et al, 2006;Stott et al, 2008;Yabe et al, 2010a, b). The presence of Ktedonobacterialike taxa in Bare cinders is consistent with results from Ranneklev and Bååth (2001), which indicate that fluctuating thermal regimes can select for and maintain thermophilic or thermotolerant communities simultaneously with mesophilic communities.…”