Study On Bacterial And Archaeal 16S RDNA Diversity In Mangrove Soil

Mangrove forests occur in the inter-tidal zones along the tropical and subtropicalcoast with the majority of Rhizophoraceae tree. Mangrove ecosystem are ecologicallycritical areas where biodiversity and valuable biological resources are highly concentrated.There exist arguments on whether "microorganism in mangrove soil are marine type orterrestrial type?" and "microorganism in mangrove soil are really rich?"In this research, total DNA were extracted directly from the soil of a mangrovereserve zone in Hainan, China, and using as template for polymerase chain reaction (PCR)amplification, which employ specific primer for Bacteria and Archaea 16S rRNA genesequences. The 16S rRNA gene libraries were then constructed. Biodiversity wereanalyzed by amplitied rDNA restriction analysis (ARDRA), DNA sequencing andphylogenetic analysis.From the results, there are sixteen phyla in Bacteria domain: Proteobacteria,Chloroflexi, Acidobacteria, Bacteroidetes, Deferribacteres, Planctomycetales,Actinobacteria, Firmicutes, Verrucomicrobia, Nitrospira, Fusobacteria, Cyanobacteria,Candidate division OP11, Candidate division WS3, Candidate division OP8 andCandidate division TM6 with the predominant phyla of Proteobacteria and Chloroflexi.In Archaea domain, it was found Crenarchaeota and Euryarchaeota kingdom andpredominate by Crenarchaeota. There are six divisions in Crenarchaeota kingdom:Marine Benthic Group A, Marine Benthic Group B, Marine Benthic Group C, MarineGroupⅠand two other groups of MSA-cluster-6 and MSA-cluster-78, which do notbelong to any already known archaea divisions. Marine Benthic Group C dominated inCrenarchaeota. There are seven divisions in Euryarchaeota kingdom: Marine BenthicGroup D,Marine Benthic Group E,Marine GroupⅣ,Rice ClusterⅠ,Rice ClusterⅢ,Methanogen (MA) and Anaerobic methane-oxidizing archaeon (ANME), dominate byMarine Benthic Group D. The results of diversity Shannon-Wiener index (H') andspecies richness (Schaol) calculated indicated that Bacteria are richer in diversity thanArchaea in mangrove soil. There are distinct differences in soil microbial community structure and diversityamong different depth. Bacterial diversity reduced with the depth increase among thedepth of 0～30 cm. a-Proteobacteria, Bacteroidetes, Actinobacteria and Candidatedivision OP11 mainly distribute in upper layer, d- andγ- Proteobacteria, Acidobacteriaand Deferribacteres are mainly distribute in middle and deep layer. Chloroflexi are mainlydistributed in upper and deep layer. With the depth increase, archaeal diversity firstincreased and then reduced, the proportion of Crenarchaeota increased andEuryarchaeota reduced.Employ a standard of using16S rDNA similarity≥97% as the same species, there areat least 76.3% of bacteria and archaea species undiscovered and 97.7% of species havenot obtained pure culture in mangrove soil. Comparing with similar studies in theliteratures indicated that microbial diversity in mangrove soil is richer than marinesediment and similar to the terrestrial soil.Comparing in the GenBank database, the most closest species to mangrove soilbacteria and archaea, 51.5% were from marine origin,. 30.1% were from connect zone ofmarine and continent origin, and 18.4% were from continent and freshwater. Mangrovesoil microbial communities appear to be a mixture of organisms found in a variety ofenvironments with the majority being of marine origin. The predominated sulphatereduction bacteria also show the characteristic of marine sediment. According to the mostrecent concept of "Microbial biogeography map", we put mangrove soil inmarine—inter-tidal—mangrove on the map.There are distinct differences in mangrove soil microbial community structure anddiversity between different vegetation. Soil microbial diversity under the imported specieSonneratia apetala is much lower than Kandelia candel, even lower than naked tidal flatsediment near mangrove. According to the sampling location in this research, it issuggested that plant Sonneratia apetala tree changed the soil microbial communitystructure and decreased microbial diversity.