| Soil microorganisms are a major component of the soil biosphere. Microbes regulate ecosystem function, and play a crucial role in the processes of ecosystem carbon and nitrogen cycles, such as the cycling of nutrient and the decomposition of organic matter, and emissions of greenhouse gases. They are the main driver of biogeochemical cycle. Changes in environmental conditions can directly or indirectly affect the microbial community compositions and function, thus affect the stability of ecosystem function. Terrestrial trophic interactions are generally dominated by microorganisms due to harsh environments, which restricts the development of higher plant communities. Furthermore soil microbes are very sensitive to the global climate changes in Arctic and Antarctica. In this paper, The soil bacterial community characteristics of typical environments in Antarctica have been studied using PCR-DGGE, cloning sequencing,454Bar-coded pyrosequencing and quantitative PCR, multi-statistical methods, combining with soil enzyme activity, microbial biomass carbon (Cmin), soil respiration. Effects of penguin and seal activities, human activities and natural ecological factors on soil bacterial community structure were detailedly discussed in the paper. This study will enrich and enlarge the research areas about polar microbiology, and will be helpful to understand the effects of soil microbes on the processes carbon and nitrogen cycles in Antarctic terrestrial ecosystems, and to predict the response and feedback of Antarctic terrestrial ecosystem to future climate changes. Main research contents and results are as follows:(1) Distribution characteristics of bacteria community in soil profile of penguins and seal colonies of east AntarcticaDistribution characteristics of bacteria community were studied in four penguin and seal colony soil profiles collected on Vesfold Hills of east Antarctica. It was found that soil Cmin, soil respiration and soil enzyme activity increased with depth in penguin and seal colonies. Overall they were much higher (one to two times) in the penguin colony than in seal colony. Bacterial abundance was significantly positively correlated with soil pH (p=0.024; p=0.048), soil moisture (p=0.021), organic carbon (p<0.001) and total nitrogen content (p<0.001), indicating that bacterial abundance was affected by the nutrients from marine animal excrement in these animal colonies.16S rDNA-DGGE molecular fingerprint and Shannon-wiener diversity index showed that the soils in penguin and seal colonies contained complex bacteria community structure. DGGE bands richness and dominant bands decreased with depths. The result of Nonmetric multidimensional scaling (NMDS) and cluster showed obvious differences in four soil profiles. The predominant bacteria bacterium categories are: Proteobacteria (36.84%), Actinobacteria (24.65%), Bacteroidetes (21.05%), Deinococcus-Thermus (5.26%), Chloroflexi (5.26%) and Firmicutes (3.51%). The results indicated that the differences of soil organic carbon, total nitrogen, pH and moisture content from marine animal excreta might be the main reasons to bacterial abundance and diversity in the soil profiles.(2) Distribution characteristics of bacteria community in soil of typical biome of western AntarcticDistribution characteristics of bacteria community were studied in six typical soils collected on Fildes peninsula of western Antarctic. It was found that soil physicochemical properties, soil invertase, phosphatase, urease activity and soil bacterial abundance were much higher in the animal colonies and human activity areas than background soils. Soil invertase and phosphatase were significantly positively correlated with soil total carbon, total nitrogen and total phosphorus content. Bacterial abundance was significantly positively correlated with soil phosphatase (p=0.006), urease (p<0.001), moisture (p<0.05), total carbon (p<0.001), total nitrogen (p=0.58), C/N (p=0.52) and total phosphorus content (p=0.35). Molecular fingerprint shows that the soils in penguin, seal colonies and human areas contained complex bacteria community structure, and some dominant bands enrichment in the upper mapping. The predominant bacteria bacterium categories are:Betaproteobacteria, Actinobacteria, Bacteroidetes, Deinococcus-Thermus, Chloroflexi, Alphaproteobacteria, Gammaproteobacteria, Acidobacteria, Gemmatimonadetes and Firmicutes, accounting for86.7%. Penguins, seals and human activity have a significant impact on bacteria community. Background regions have a high bacteria phylogenetic diversity (PD=85.79) and phylotype richness (OUT=976), whereas animal and human activities reduce the diversity. Pearson correlation analysis showed that soil TN (p=0.0031; p<0.001), TC (p=0.011; p=0.0024), C/N (p=0.031; p=0.0028) and Zn (p=0.030; p=0.025) contents are the major environmental factors affecting soil bacteria phylogenetic diversity and phylotype richness. The relative abundance of Bacteroides were significantly positively correlated with soil carbon and nitrogen (p=0.003; p=0.007), with a negative correlation for the relative abundance Betaproteobacteria and Actinobacteria.(3) The Y2lake sedimentary section bacteria changes and the historical relationship of climate changeDistribution characteristics of bacteria community were studied in sediments collected on Y2lake sediment of Fildes peninsula, western Antarctic. It was found twelve kinds of physicochemical indicators show a high consistency with depth change and were divided into four regions:0to7cm, the surface is high, and decreases with depth;7to23cm, increases with depth slowly;23to34cm, significantly reduced, the lowest value in the32cm;34to48cm, increase with depth. The whole fingerprint can be divided into three regions:1to22cm, without a big change in the overall stripe;23to36cm obviously increasing in bands richness and dominant bands;37to48cm without a large range. Bacterial abundance in depth distribution was also divided into four sections:the first surface containing a high bacteria abundance and decreasing with depth (0to8cm); the second section slowly increasing until23cm; the third section with a significant increase (23to32cm); the last one a slowly lower increasing speed (32to48cm), and thus the maximum appeared in the32cm. The advantage of bacteria bacterium categories are: Betaproteobacteria, Actinobacteria, Gemmatimonadetes, Bacteroidetes, Acidobacteria, Gammaproteobacteria and Chloroflexi, occupy87.2%of all. Combination of physicochemical properties, DGGE fingerprint, quantitative PCR, and454sequencing results, we found the penguin populations and excretion significantly affect the diversity of bacterial community structure in the sedimentary.(4) Phosphatase activity characteristics in soil profiles and effects on the phosphorus cycleAlkaline phosphatase activity (APA) were determined in the soil profiles collected from Vesfold Hills, Lasemann Hills in east Antarctica, and Ny-Alesund in Arctic. Soil APA showed a regular distribution with depths, the maximum appeared in surface soil layers, and then decreased with depths. APA showed a significant positive correlation with soil organic carbon, total nitrogen contents, and the contents of phosphorus fractions, whereas soil APA showed a negative correlation with Cu and Zn contents, suggesting that heavy metals might limit the soil APA. Phosphine increased first in soil surface layer and then decreased with depth. Alkaline phosphatase was significantly affected phosphine along with the profile distribution. Overall, the activity of soil phosphorus was mostly affected by carbon, nitrogen and the other organic matters in the polar regions, and thus soil phosphatase activity can be used as an important indicator for soil microbial activity and soil fertility. |
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