A Preliminary Study On The Community Structure And Function Of The Antarctic Ice Algae Chlamydomonas Sp.ICE-L

Antarctic ice algae inhabit in sea ice.In order to understand the relationships between symbiotic bacteria and ice algaeunderfreezing temperature stress.The composition of bacterial community associated with Chlamydomonas sp.ICE-L were studied,and the results were as follows:(1)Kanamycin,ampicillin,chloramphenicol,cephalosporin,rifampicin,streptomycin and gentamycin sulfate were used to treat the symbiotic system of Antarctic ice algae.The results showed that the seven antibiotics had obvious inhibitory effects on the symbiotic bacteria of Antarctic ice algae at the concentration of 1000 ? g/mL,and cephalosporin,chloramphenicol and rifampicin had obvious inhibitory effects at three concentrations.The other four antibiotics were not inhibited at the concentration of 100? g/mL,and the concentration of 50 ? g/mL had a promoting effect.The mixed antibiotics obviously promoted the growth of Antarctic ice algae.(2)The symbiotic bacteria of Antarctic ice algae mainly constituted with Proteobacteria and Bacteroidetes at the phylum level.At the genus level,the bacterial communities were predominated by Psychroflexus,Sulfitobacter,Maribacter,Thalassobaculum,Halomonas and Methylophaga,Psychroserpens,Nonlabens,Marinobacter,Sphingorhabdus and Algimonas.(3)The constitutions of the symbiotic bacterial community of Antarctic ice algae culture at freezing(-20?),normal growth temperature(4?)and high temperature(15 ?)were studied.It was found that the dominant bacteria varied greatly in the genus level at different temperatures,and the content of symbiotic bacteria of the same genus fluctuated at the same temperature and different culture time.The dominant genera at-20? are Thalassobaculum,Psychroserpens and Nonlabens.The dominant bacteria under 4? was Marinobacter,while the dominant bacteria under 15? was Algimonas.(4)The six symbiotic bacteria isolated from the Antarctic ice algae culture were co-cultured with C.reinhardtii.The results showed that the six symbiotic bacteria were psychrophilic or psychrotrophic bacteria and could remain active at-20 ?.Culture experiments showed that the six Antarctic ice algae symbiotic bacteria had different effects on the survival rate of C.reinhardtii under freezing conditions.The results of photosynthetic efficiency measurement showed that the symbiotic bacteria did not enhance the ability of C.reinhardtii to survive at low temperature by enhancing the photosynthetic efficiency.(5)The whole genome of the Antarctic ice algal symbiosis Nonlabens sp.Ci31 wassequenced.The genome sequence was uploaded to NCBI and the registration number was CP043633.The optimal growth temperature of Nonlabens sp.Ci31 is 15?.It is a psychrotrophic,motility bacterium.The whole genome contains a 3,740,082 bp round chromosome with G+C content of 36.68 % without plasmid.There are three RNA operons,36 tRNA genes and eight gene islands in the genome.Total1888,2127 and 2950 genes in the genome of Ci31 were annotated by GO,COG and KEGG database,respectively.