Unveiling the genomic aspects of Hahella chejuensis KCTC2396, an algicidal marine bacterium

Abstract

Hahella chejμeηsis KCTC 2396T, previously identifìed as a sole member of a novel genus (Lee et al, 2001, IJSEM 51:661-6) in the class gammmaproetobacteria， produces copious extracellular polysaccharides having desirable properties for industrial applications and a red pigment showing the algicidal activity against Coch!odinium and other red-tide phytoplanktons. Random shotgun sequences of about 5.3-fold genomic coverage were assembled into 619 contigs (total contig length ≈ 7.3 Mb), and basic annotation was performed. Arnong the 7,376 ORFs predicted by Glimmer, 45% could be functionally assignable according to the COG categories, and 30% were unique to the genome. Genes potentially involved in synthesis of red pigments were searched throl..1ghout the genome, and several were identified in a scaffold consisting of four contigs. Subsequently, a ca. 60-kb region encompassing all of the genes responsible for 52 the pigment synthesis was completely sequenced and re-annotated. Genome analysis also revealed a multitude of genes possibly involved in biosynthesis and transport of exopolysaccharides, and about a dozen of gene clusters for biosynthesis of polyketides and non-ribosomal peptides. One of the striking features of the H. chejueneis genome is the unexpected presence of two gene sets for type III secretion, which functions in injection of effector proteins into eukalyotic cells. This suggests that H. chejueneis may occupy a unique ecological position in the marine environment through interactions with oLher organisms.