Polyphasic Taxonomy Of Two Novel Bacteria Isolated From The Antarctic Intertidal Sediments

The Antarctic continent and its adjacent sea areas, contain many unique microorganisms because of the very special geographical and climatic conditions. These microbes are novel and extremely diverse in terms of their species, physiologies, metabolisms and ecological functions and have great values in scientific researches and broad application prospects. Finding and identifications of new Antarctic bacteria are the prerequisites to study and exploit the Antarctic microorganism resources.In this work, two bacterial strains were isolated from Antarctic intertidal sediment and were subjected to polyphasic taxonomic studies. Based on the data obtained, the two strains were proposed to represent two novel species in two baterial genera.1. Polyphasic taxonomy of strain ZS2-30Strain ZS2-30was isolated from Antarctic intertidal sandy sediment. Cells of strain ZS2-30are Gram-negative rods (1.5-2.3μm in length and0.5-0.8μm in width) and motile by means of a single polar flagellum. Colonies on TYS agar are cream-colored, circular (1.5-2.0mm in diameter), convex with smooth surfaces. The major fatty acids of strain ZS2-30are summed feature3(C16:1ω7c and/or iso-C15:02-OH), C16:0, C18:1ω9c, C16:1ω9c, and C12:03-OH and The predominant respiration quinone was Q-9. The major polar lipids of strain ZS2-30were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and an unidentified aminophospholipid. Genomic DNA G+C content of strain ZS2-30was55.8mol%.Analyses of16S rRNA gene sequences revealed that strain ZS2-30was affiliated with the genus Marinobacter. It showed highest16S rRNA gene sequence similarities to the type strains of three Marinobacter species, namely Marinobacter maritimus (98.3%), M. psychrophilus (98.1%) and M. goseongensis (97.1%), but the DNA-DNA relatedness between strain ZS2-30and the above three Marinobacter species were all lower than45%. Moreover, strain ZS2-30could be distinguished from closely related Marinobacter species by various phenotypic properties such as nitrate reduction and melanin production from tyrosine. Based on the polyphasic taxonomic evidences presented in this study, strain ZS2-30is considered to represent a novel species in the genus Marinobacter, for which the name Marinobacter antarcticus sp. nov. is proposed. The type strain of Marinobacter antarcticus is ZS2-30(=CGMCC1.10835T=KCTC23684T).2. Polyphasic taxonomy of strain ZS3-33Strain ZS3-33was isolated from Antarctic intertidal sediment. Cells of strain ZS3-33are Gram-negative, non-motile rods (1.0-2.5μm in length and0.5-0.8μm in width). Colonies on TYS agar are pink, circular (1.0-1.5mm in diameter), convex with smooth surfaces. The major cellular fatty acids of Strain ZS3-33was ummed feature8(comprising C18:1ω7c and/or C18:1ω6c) and the major respiratory quinone was Q-10. The predominant polar lipids Strain ZS3-33were phosphatidylglycerol, phosphatidylcholine, two unidentified aminophospholipids and one unidentified aminolipid. Genomic DNA G+C content of strain ZS3-33was57.1mol%.Analyses of16S rRNA gene sequences revealed that strain ZS3-33belonged to the genus Pseudorhodobacter, showing97.4%16S rRNA gene sequence similarity to type strain of Pseudorhodobacter ferrugineus and95.3%to P. aquimaris. GyrB gene sequence similarities of strain ZS3-33to type strains of P. ferrugineus and P. aquimaris were87.6%and81.7%, respectively. DNA-DNA relatedness between strain ZS3-33and P. ferrugineus DSM5888T was56.6%. Besides, strain ZS2-30could be distinguished from closely related Pseudorhodobacter species by several phenotypic properties such as nitrate reduction, colony color and optimal growth temperature. Based on the polyphasic data in this study, strain ZS3-33represents a novel species of the genus Pseudorhodobacter, for which the name Pseudorhodobacter antarcticus sp. nov. is proposed. The type strain is ZS3-33(=CGMCC1.10836T=KCTC23700T).