Erwinia endophytica sp. nov., isolated from potato (Solanum tuberosum L.) stems.

We analysed, using a polyphasic taxonomic approach, two bacterial strains coded BSTT30T and BSTT40, isolated in the course of a study of endophytic bacteria occurring in the stems and roots of potatoes growing in soil from Salamanca, Spain. The 16S rRNA gene sequence was identical in both strains and had 98.4 % identity with respect to the closest relatives Erwinia tasmaniensis Et1/99T and Erwinia rhapontici ATCC29283T. Erwinia billingiae E63T and Erwinia toletana A37T were also closely related with 98.2 % sequence similarities, so the novel strains were classified within the genus Erwinia. The analysis of the housekeeping genes gpd, gyrB and rpoD confirmed the phylogenetic affiliation of strains BSTT30T and BSTT40 with similarities of lower than 90 % in all cases with respect to the closest relatives mentioned above. The respiratory quinone of strain BSTT30T was Q8. The major fatty acids were C16 : 0, C16 : 1ω7c/16 : 1ω6c in summed feature 3 and C18 : 1ω7c/18 : 2ω6,9c in summed feature 8. The novel strains were oxidase-negative and catalase-positive. Glucose was fermented without gas production. They were negative for arginine dihydrolase, urease and indole production. The strains could grow at 35 °C and at pH 10. DNA G+C content was 50.1 mol%. DNA-DNA hybridization results showed values of lower than 29 % relatedness with respect to the type strains of the four most closely related species. Therefore, the combined genotypic, phenotypic and chemotaxonomic data support the classification of strains BSTT30T and BSTT40 into a novel species of the genus Erwinia, for which the name Erwinia endophytica sp. nov. is proposed. The type strain is BSTT30T ( = LMG 28457T, CECT 8692T).