Micromonospora halotolerans sp. nov., isolated from the rhizosphere of a Pisum sativum plant.

A filamentous actinomycete strain designated CR18(T) was isolated on humic acid agar from the rhizosphere of a Pisum sativum plant collected in Spain. This isolate was observed to grow optimally at 28 °C, pH 7.0 and in the presence of 5 % NaCl. Phylogenetic analyses based on the 16S rRNA gene sequence indicated a close relationship with the type strains of Micromonospora chersina and Micromonospora endolithica. A further analysis based on a concatenated DNA sequence stretch of 4,523 bp that included partial sequences of the atpD, gyrB, recA, rpoB and 16S rRNA genes clearly differentiated the new strain from recognized Micromonospora species compared. DNA-DNA hybridization studies further supported the taxonomic position of strain CR18(T) as a novel genomic species. Chemotaxonomic analyses which included whole cell sugars, polar lipids, fatty acid profiles and menaquinone composition confirmed the affiliation of the new strain to the genus Micromonospora and also highlighted differences at the species level. These studies were finally complemented with an array of physiological tests to help differentiate between the new strain and its phylogenetic neighbours. Consequently, strain CR18(T) (= CECT 7890(T) = DSM 45598(T)) is proposed as the type strain of a novel species, Micromonospora halotolerans sp. nov.