| In this experiment,five soil samples collected from the Biological Bay basin of the fields peninsula in Antarctica were used to study the diversity of culturable nitrogen cycling bacteria(including nitrogen-fixing bacteria,ammoniation bacteria,nitrifying bacteria and denitrifying bacteria),on bacterial count of samples,isolation and purification of strains,morphological observation,enzyme-producing activity,phylogenetic analysis of 16 S r RNA gene,etc..Meanwhile the diversity analysis of high-throughput sequencing on key functional genes of nitrogen cycle(including nitrifying bacteria gene nxr A,denitrifying bacteria gene nir S,nitrogen-fixing bacteria gene nif H,and ammoniation bacteria gene amo A)were also carried out.The purpose of this study is to understand the diversity composition and distribution characteristics of nitrogen cycle bacteria in this special ecological region,and to lay a foundation for further research on their ecological adaptability.In addition,we also expect to find the low-temperature and high-efficiency enzyme-producing strains or new species,which will add valuable strains for the follow-up applied research and enrich the polar bacterial taxa.1.The results of the study on culturable nitrogen cycle bacteria showed that: The total numbers of nitrogen circulating bacteria in four soil samples were ammoniation bacteria(1.08×108-1.82×109)> nitrifying bacteria(1.96×105-8.82×107)and denitrifying bacteria(2.00×106-3.48×107)> nitrogen-fixing bacteria(6.7×105-4.4×106).Most isolated strains had the activities of producing DNA enzyme,amylase,catalase,casein hydrolase,heptaginine hydrolase,cellulase,oxidase,and degrading Twain,and there are some strains with high enzyme producing activity in these enzyme producing strains.The order of 16 S phylogenetic diversity were as follows: ammoniation bacteria(3 classes,6genera)> nitrogen-fixing bacteria(2 classes,4 genera),nitrifying bacteria(2 classes,3genera)> denitrifying bacteria(1 class,4 genera).Among it,Pseudomonas was the dominant group in each group of bacteria.In addition,it was found that the similarities of16 S r DNA sequences of 9 strains were less than 97%(85.77-96.88%)compared with that of model bacteria,which may be some potential new species or new genus.2.The results of high-throughput sequencing on key functional genes of nitrogen cycle bacteria showed that:(1)In high-throughput sequencing of the nitrifying bacteria gene snxr A,there were 4 common classes and 3 common genera in SWW1?SWW2?SWW3?SWW4?SWWC1 samples.Among them,the sample SWW2(seal activity and rest area)has the most species at the class and genus levels,and SWW1(near the intertidal zone)has the least.The distribution types of dominant bacterial flora in the 5 samples were different.Principal component PCo A analysis showed that,at the levels of class and genus,the similarity of the bacterial community composition of samples SWW1 and SWW4(away from the coast and near the iceberg)was the closest.Sample SWWC1(intertidal zone)was special,which was far away from the other four samples on bacterial community composition,and had some classes and genera not found in other samples.(2)In high-throughput sequencing of the denitrifying bacteria gene snir S,there were 7common classes and 7 common genera in 5 samples.Sample SWW2 and SWW3(areas of moss-covered and a few seal)had relatively high denitrifying bacteria species diversity at the levels of class and genus,while many classes and genus did not exist in the other three samples.The distribution types of dominant bacterial flora in the 5 samples were different.Principal component PCo A analysis showed that,at the levels of class and genus,the similarity of the denitrifying bacterial community composition between SWW1 and SWW4 is similar,as was the case between SWW2 and SWW3,but SWWC1 was far away and particularity.(3)The results of high-throughput sequencing of nitrogen-fixing bacterial gene nif H showed there were 6 common classes and 7 common genera in 5samples.At the class and genus levels,sample SWW2 and SWW3 also had relatively high species diversity of nitrogen-fixing bacteria.The distribution types of dominant bacterial flora in the 5 samples were different.The principal component PCo A analysis showed that sample SWW3 and SWWC1 were particularity in community composition similarity of nitrogen-fixing bacteria,which was different from that of nitrifying bacteria and denitrifying bacteria.(4)The results of high-throughput sequencing of amonifying bacteria gene amo A showed that samples SWW2,SWW3,SWW4 and SWWC1 had relatively high diversities of ammoniated bacteria at the class and genus levels,but SWW1 was the least(only 3 classes and 3 genera).Principal component PCo A analysis showed that the samples SWWC1,SWW1 and SWW2 were particularity in community composition similarity of ammoniated bacteria.3.The polyphasic taxonomy results of marine new bacteria H164 T isolated from the Caroline Seamount in the Western Pacific showed that strain H164 T was spherical,Gram-negative and facultative anaerobic.Its 16 S r RNA gene similarity was 97.4%compared to that of the most recent model strain A.wandonensis WS-MY22 T of the genus Algibacter.Its DNA G+C content was 33.2 mol%,the main fatty acid composition were iso-C15:0,iso-C15:1 G,iso-C15:0 3-OH and iso-C17:0 3-OH.The main respiratory quinone was MK-6.The main polar lipid component were 1 phosphatidyl ethanolamine,1aminolipid and 2 unknown lipids.The other physiological and biochemical characteristics of strain H164 T were also unique.Combined with the characteristics of genetic,physiological,biochemical,and chemical of strain H164 T,as well as whole genome sequence data analysis,We were sure that strain H164 T was a new species of the genus Algibacter,named Algibacter pacificus sp.nov. |
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