Marinilactibacillus piezotolerans sp. nov., a novel marine lactic acid bacterium isolated from deep sub-seafloor sediment of the Nankai Trough

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Abstract
A piezotolerant, mesophilic, marine lactic acid bacterium (strain LT20T) was isolated from a deep sub-seafloor sediment core collected at Nankai Trough, off the coast of Japan. Cells were Gram-positive, rod-shaped, non-sporulating and non-motile. The NaCl concentration range for growth was 0–120 g l−1, with the optimum at 10–20 g l−1. The temperature range for growth at pH 7·0 was 4–50 °C, with the optimum at 37–40 °C. The optimum pH for growth was 7·0–8·0. The optimum pressure for growth was 0·1 MPa with tolerance up to 30 MPa. The main cellular phospholipids were phosphatidylglycerols (25 %), diphosphatidylglycerols (34 %) and a group of compounds tentatively identified as ammonium-containing phosphatidylserines (32 %); phosphatidylethanolamines (9 %) were minor components. The fatty acid composition was dominated by side chains of 16 : 0, 14 : 0 and 16 : 1. The G+C content of the genomic DNA was 42 mol%. On the basis of 16S rRNA gene sequence analysis and the secondary structure of the V6 region, this organism was found to belong to the genusMarinilactibacillusand was closely related toMarinilactibacillus psychrotoleransM13-2T(99 %),Marinilactibacillussp. strain MJYP.25.24 (99 %) andAlkalibacterium olivapovliticusstrain ww2-SN4C (97 %). Despite the high similarity between their 16S rRNA gene sequences (99 %), the DNA–DNA hybridization levels were less than 20 %. On the basis of physiological and genetic characteristics, it is proposed that this organism be classified as a novel species,Marinilactibacillus piezotoleranssp. nov. The type strain is LT20T(=DSM 16108T=JCM 12337T).

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