Marinobacter alexandrii sp. nov., a novel yellow-pigmented and algae growth-promoting bacterium isolated from marine phycosphere microbiota

The marine phycosphere harbors unique cross-kingdom associations with ecological relevance. During investigating the diversity of phycosphere microbiota of marine harmful algal blooms dinoflagellates, a faint yellow-pigmented bacterium, designated as strain LZ-8, was isolated from paralytic shellfish poisoning toxin-producing dinoflagellate Alexandrium catenella LZT09. The new isolate appeared to have growth-promoting potential toward its algal host. Molecular analysis using 16S rRNA gene, housekeeping rpoD gene and whole-genome sequence comparison indicated that strain LZ-8(T) was a novel gammaproteobacterium of the family Alteromonadaceae. The major fatty acids of strain LZ-8(T) were C-16:0, C-18:1 omega 9c, C-12:0 3-OH, summed feature 3, C-16:1 omega 9c, C-12:0 and summed feature 9. The major isoprenoid quinone was Q-9. Polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, unidentified phospholipid, two unidentified aminolipids and six unidentified polar lipids. The genomic DNA G+C content was 57.36 mol%. Based on genome sequencing, several biosynthetic gene clusters responsible for bacterial biosynthesis of carotenoids and siderophores that may involve in algae-bacterial interactions were identified in the genome of strain LZ-8(T). The polyphasic characterization indicated that strain LZ-8(T) represents a novel Marinobacter species. The name Marinobacter alexandrii sp. nov., type strain LZ-8(T) (= CCTCC AB 2018386(T) = KCTC 72198(T)) is proposed.