Elusimicrobium minutum Pei191

Elusimicrobium minutum (strain Pei191) is a mesophilic, obligately anaerobic free-living ultramicrobacterium with a Gram-negative cell envelope isolated from the intestinal cluster from the hindgut of a humivorous scarab beetle larva. Cells are typically rod shaped, but cultures are pleomorphic in all growth phases. E.minutum grows heterotrophically on sugars and ferments D-galactose, D-glucose, D-fructose, D-glucosamine, and N-acetyl-D-glucosamine to acetate, ethanol, carbon dioxide, hydrogen, and alanine as major products but only if amino acids are present in the medium. The production of alanine from glucose is unusual. Alanine is not formed from other amino acids present in the medium but is, rather, derived from the carbon skeleton of glucose. E. minutum does not grow on amino acids, either by fermentation of single amino acids or by fermentation of amino acid pairs (Stickland reactions). Instead, it ferments amino acids only during growth on glucose, presumably by transamination with pyruvate and subsequent oxidative decarboxylation of the resulting 2-oxoacid. This leads the formation of the corresponding oxidative decarboxylation product from most proteinogenic amino acids and the net formation of alanine concomitant to the disappearance of the respective amino acid from the medium. On basal medium with glucose, the cells grow within a pH range of 6.2 to 8.2, and a temperature range of 20 to 32 degrees Celsius but not at 15 or 37 degrees Celsius. Highest growth rates are obtained at 30 degrees and pH 7.5. Growth is best in freshwater medium, but E. minutum also grows at 3.5% salt concentration. PCR-based screening and comparative 16S rRNA gene sequence analysis revealed that strain Pei191 belongs to the intestinal cluster (cluster III) of the Elusimicrobia phylum, a lineage of hitherto uncultivated bacteria present in arthropod and mammalian gut systems. It is only distantly related to the so-called endomicrobia lineage, which comprises mainly uncultivated endosymbionts of termite gut flagellates. (Adaptated from PMID: 19270133, 19270135). (EBI Integr8)