Paenibacillus lentus sp. nov., a β-mannanolytic bacterium isolated from mixed soil samples in a selective enrichment using guar gum as the sole carbon source.

A novel bacterial strain, CMG1240(T), was isolated in 1988 from mixed soil samples collected from the United States and South America in a selective enrichment medium with guar gum as the sole carbon source. This microbial isolate showed β-mannanolytic activity to hydrolyse the galactomannans present in guar gum. Strain CMG1240(T) was aerobic, Gram-stain-variable, non-motile, rod-shaped and endospore-forming. It was further examined based on a combination of phenotypic, physiological and genetic characterization. On the basis of 16S rRNA gene sequence similarity, cellular lipid profile and fatty acid composition, strain CMG1240(T) was shown to belong unequivocally to the genus Paenibacillus. Quinone analysis showed that MK-7 was the only menaquinone detected. The main cell-wall sugar was xylose with trace amounts of mannose and glucose. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and unknown glycolipids, phospholipids, phosphoglycolipids and other lipids. The peptidoglycan structure was A1γ (meso-diaminopimelic acid-direct). The major fatty acids were anteiso-C15 : 0 and C16 : 0. The DNA G+C content was 46 mol% as determined experimentally and by analysis of the genomic sequence. The 16S rRNA gene sequence of strain CMG1240(T) shared highest similarity with that of Paenibacillus fonticola ZL(T) (97.6 %) while all other tested Paenibacillus strains showed lower sequence similarities (≤95.3 %). The results of DNA-DNA hybridization and chemotaxonomic tests enabled the genotypic and phenotypic differentiation of strain CMG1240(T) from P. fonticola. Based on these results, strain CMG1240(T) ( = ATCC BAA-2594(T) = DSM 25539(T)) should be designated the type strain of a novel species within the genus Paenibacillus, for which the name Paenibacillus lentus sp. nov. is proposed.