Diversity Of Nitrogen Cyclebacteriain Soils Of Penguin Island, Fildes Peninsula, Antarctica

The eastern and western sides of Penguin Island,located in the Fields Peninsula,Antarctica,have distinct ecological characteristics.In this study,10 soil samples(including 2 intertidal sediment samples)were collected from the east and west sides of Penguin Island.By the approaches of selective cultivable methods and high-throughput sequencing methods based on 16S rRNA gene and key functional genes of nitrogen-cycling bacteria(nitrification gene nxr A,denitrification gene nirS,ammonia oxidation gene amoA,nitrogen fixation gene nifH),we research the strain counts of samples,morphological observation and enzyme-producing activity of isolated strains,functional activity of nitrogen cycling bacteria,and the compositions of bacterial groups of samples.The purposes are to comprehensively understand the diversity composition and difference of nitrogen cycling bacteria on the east and west sides of Penguin Island,find the strains with high activity of enzyme production or nitrogen cycling,and hope to discover new species taxa.This study can provide a reference for the related researches in other similar regions of Antarctica,and provide valuable strains for the subsequent application research.The results showed:(1)In general,the nitrogen circulating bacteria content of samples from the east side of Penguin Island(including intertidal samples)was higher than that of samples from the west side of this island(including intertidal sediments).The morphological diversity of ammoniating bacteria was higher than that of nitrifying bacteria,denitrifying bacteria and nitrogen-fixing bacteria.(2)On the whole,the diversities of nitrogen circulating bacteria and common bacteria in the east and west sides of Penguin Island were all relatively high.At the genus level,the diversity of general culturable nitrogen cycling bacteria in the east side soils of Penguin Island was much higher than that of the west side of this island.However,the diversity of the high-throughput nitrogen cycling bacterial flora from the west side of Penguin Island was generally higher than that from the east side of this island,but for some samples on either side of Penguin Island,the bacterial flora abundances were reversed.In addition,soil physical and chemical factors TOC and TON generally had a greater influence on the flora composition of nitrifying bacteria,denitrifying bacteria,nitrogen-fixing bacteria and ammoniating bacteria in all samples(On the whole,there was a positive correlation between the bacterial species composition on the west side of the island and a negative correlation between the bacterial species composition on the east side of the island).NO₂^--N and PO₄^3--P had great influence on nitrifying bacteria in intertidal samples,NH₄⁺-N had great influence on nitrogen fixing bacteria in QED-3 samples in the west of the island,NH₄⁺-N and NO₂^--N had great influence on species composition of ammonifying bacteria in QEC-2,QED-2 on the west side of the island and QE-1 in the east of the island.These differences were speculated to be mainly caused by the distinct ecological environments on both sides of Penguin Island and the different sensitivities of the two research approaches and methods.(3)We found some strains with strong activities of producing DNA enzyme,amylase,casein hydrolase,and heptinase,as well as strains with strong ammoniation and denitrification functions.Meanwhile,we also found that 40 strains of nitrogen cycling isolates could be potential new species groups or new genus groups,which are worthy of further classification.This study provides some reference for similar studies in other similar regions of Antarctica,and provides the strain basis for related application research in the future.