Diversity Of Bacteria In Surface Sediments From Wudalianchi Volcanic Lake And Their Relationship To Environmental Factors

Biodiversity of microorganisms in sediments has become a hotspot and focus on molecular ecology of microorganism in water body.The sediment is the ideal habitat for microorganism due to its abundant nutrition and special environment.Magnetotactic bacteria(MTB),the members of sediment microorganisms,play an important role in geochemical cycles of iron-sulfur elements and the soilmagnetism of sediments.The analysis of the biodiversity of microorganisms in sediments only focuses on freshwater habitats and brackish habitats in recent years,and there is lack of the microbiodiversity of sediments in volcanic lakes.Additionally,the study of MTB in sediments only focuses on the biodiversified analysis,their effect on the magnetic properties of sediments is seldom reported.And what's more,the molecular geography of bacteria in sediments including MTB mainly focuses on the single water body or the large-scale water bodies,lacking a systematic study on the diversity of bacteria including MTB in different types of water body on smaller scale.Aiming at the above background,this study selected eight volcanic lakes in Wudalianchi to analyze the physicochemical characteristics of their surface sediments,and the magnetic enrichment and Race-track technology were used to collect MTB and non-magnetotactic bacteria.Next-generation sequencing was used to explored the diversity of MTB and non-magnetic bacteria in sediments.The relationship between the diversity of bacteria and sediment environmental factors was investigated to reveal the environmental significance of bacteria in sediments.The frequency magnetic susceptibility,room temperature magnetic analysis and low temperature magnetic analysis of sediments before and after magnetic collection were tested by environmental magnetism technology the influence of MTB on the magnetic properties of the sediments was obtained by the difference between before and after magnetic collection.Results of physicochemical analysis showed that the soluble total iron,sulfide,total phosphorus,total nitrogen,total organic carbon,ammonia nitrogen and salinity in 12 environmental factors of eight volcanic lakes were significant different.Total nitrogen,SO42-,Fe2+,salinity and nitrate nitrogen were the main influencing factors in distinguishing different types of water body.Principal Component Analysis of environmental factors shown that YQH and WC were similar,YC and EC were also similar.The results of MTB diversity analysis indicated that Proteobacteria was dominant species in phylum level in each sample while there were significant differences in genus level.Crenothrix was dominant species in YYP and YQH,but its abundance was different,the proportion of YYP was 14.83% and YQH was 20.62%.The dominant bacteria in WB was Nitrospira(16.21%),Magnetospirillum(31.28%)was dominant in YC,the dominant bacteria in EC and FC were both Alphaproteobacteria,and theirs abundance are 4.27% and 25.56%,respectively.The dominant bacteria in SC and WC separately were Staphylococcus(19.33%)and Methylophilaceae(63.71%),respectively.The correlation between MTB diversity and environmental factors showed that the dominant bacteria Proteobacteria were positively correlated with the soluble total iron,sulfide,total organic carbon,total nitrogen and ammonia nitrogen,and negatively correlated with total phosphorus and salinity.It was found that YQH and YC are similar in species composition,FC,WC and YYP are also similar in species composition.The magnetic properties of sediments before and after magnetic collection by using environmental magnetism methodsto elaborate the effect of MTB on the magnetic properties of sediments Results shown that MTB has different effects on frequency magnetic susceptibility,room temperature magnetic analysis and low temperature magnetic analysis of sediments in different lakes.There was significant difference in the frequency susceptibility between EC and the other seven lakes.The magnetization of the eight lacustrine sediments were different in the range of 0-15000 Oe.The low-temperature magnetization of sediments in 8 volcanic lakes were different in a certain temperature range.The results of non-magntotactic bacteria diversity revealed that the dominant species were different in each sample in phylum level.In genus level the dominant specie in YYP was Arthrobacter,and its abundance was 14.83%,the dominant bacteria in YQH and EC were both Nitrospira(16.21%),and their abundance were 4.35% and 3.89%,respectively.Dominant species in WB,YC and WC were Thiobacillus(22.04%),Gemmatimonas(5.99%)and Lactobacillus(6.57%).It also can be found that Candidatus-Solibacter was dominant bacteria in SC and FC,the proportions were 6.38% and 9.51%,respectively.The correlation between non-MTB diversity and environmental factors shown that Proteobacteria was positively correlated with total phosphorus,and negatively correlated with ammonia nitrogen,salinity,total organic carbon,soluble total iron,sulfide and total nitrogen.Results also indicated that the YQHand SC are similar in species composition,YC,FC and YYP are similar in species composition.In summary,there are abundant bacterial groups in the volcano lake of Wudalianchi.MTB and non-magnetic bacteria mainly distributed in 15 phylums and 12 phylums,respectively,MTB and non-magnetic bacteria distribution were different in different lakes.The distribution of MTB were significantly influenced by soluble total iron and sulfide.Total phosphorus,total organic carbon and total nitrogen significant effected the distribution of non-magnetotactic bacteria.The distribution characteristics of bacteria in sediments of Wudalianchi volcanic lakes might be caused by environmental factors and/or the types of water body.The magnetic properties of the surface sediments of volcanic lakes were significantly affected by MTB.