| In this research, mangrove swamp has been selected as a research region in Fugong, Longhai, Fujian Province of China to study the potential role in bioremediation of polluted environment. The four transects including sixteen stations were established, and the surficial sediments were collected in Winter and Summer, respectively. Physico-chemical and microbiological parameters were determined in 16 stations from mangrove swamps. The activities of extracellular enzymes were analyzed, and the changes of microbial community constructure were also evaluated when added different PAHs to the samples from mangrove sediments. In addition, according to PCR-DGGE profiles, the research of degradation characteristics of individual and mixed PAHs have been performed by different mixture of PAH-degrading bacteria isolated from mangrove swamp.The results obtained are summarized as follows:1. The physico-chemical parameters were determined in mangrove surficialsediments from 16 stations, such as pH, salinity, temperature, TOC, TOM, and contents of oil. The glucosidase activities and PAHs contents were also determined in different stations by the method of fluorogenic model substrate (FMS) and GC/MS, respectively. The activities of a-glucosidase (α-GlcA) ranged from 10.63μmol/gh to 100.86μmol/gh and from 43.80μmol/gh to 197.78μmol/gh in Winter and Summer, respectively, and the activities ofβ-glucosidase (β-GlcA) varied from 39.60μmol/gh to 222.75μmol/gh in Winter and from 169.88μmol/gh to 676.93μmol/gh in Summer. There was significant positive relationship betweenα-GlcA andβ-GlcA (R~2=0.8215 and R~2=0.7582), andβ-GlcA was higher thanα-GlcA in different seasons. The significant positive relationship was found between glucosidase activities and TOC, also TOM. Except, there was no significant relationship between glucosidase activities and other environmental parameters. The contents of PAHs ranged from 279.98 ng/g to 1074.50 ng/g,and HMW PAHs were dominant in all of the stations. Based on our data, it suggested the source of PAHs maybe came from fuel combustion.2. The numbers of several different bacterial groups, including culturable heterotrophic bacteria, Phe-degrading bacteria, Pyr-degrading bacteria, Flu-degrading bacteria, Bap-degrading bacteria and mixture of PAH-degrading bacteria were counted. Correlated relationship was analyzed between bacterial numbers and environmental parameters. The results showed the numbers of these bacteria were higher in Summer than those in Winter. As to the numbers of culturable heterotrophic bacteria, there was different relationship between them and the environmental parameters in different seasons, and significant positive relationship between them and glucosidase activities. While, there were no differences in correlations between the numbers of PAH-degrading bacteria and contents of PAHs.The results of analysis of microbial community structure by the method of PCR-DGGE indicated that the diversity of microbial population was higher in Summer than that in Winter by DGGE profiles. The microbial diversity was also higher in mangrove swamp than that in non-mangrove swamp. There were various Shannon-wiener Index (H), Richness (S), Evenness (EH) and community similar coefficient in mangrove sediments at different stations.The results of evaluation to microbial diversity by the method of constructed 16S rDNA library showed that the most colonies were uncultured microbes in 16S rDNA library. The dominant microbes belonged to Proteobacteria (70.0%), the other microbes were Bacteroidetes (8.0%), Planctomycetacia (2.0%), Actinbacteria (2.0%) and Verrucomicrobia (2.0%), respectively. Additional, uncultured and unclassified microbes (16.0%) were also detected. Finally, it demonstrated that there were abundant microbial diversity in mangrove sediments by using the methods of either PCR-DGGE or 16S rDNA library.3. The results of research on community structure through the response of microbes in mangrove swamp under PAHs stress revealed that different changes of microbial community structure had occurred in different concentrations of Phe, Pyr, Flu, Bap and M-PAHs. The more obvious influence would happen to microbial community structure in higher concentrations of PAHs, and responsive time would also be short. The most bands of distinct difference were as uncultured microorganisms that were associated with biodegradation of pollutants.4.14 strains of PAH-degrading bacteria were isolated from mangrove sediments in Winter. All of these strains belonged to Proteobacteria, includingα-proteobacteria (7 strains, 50%) andγ-proteobacteria (7 strains, 50%). Based on microbial morphology and results of RFLP analysis, 67 strains PAH-degrading bacteria were isolated from mangrove swamp in Summer by some screening strategies with different medium. All of them were chosen to carry out 16S rDNA identification. The results indicated that these strains were grouped into four phylum from samples in Winter and Summer, including 38 strains of proteobacteria (α-proteobacteria, 14 strains;β-proteobacteria,1 strains;γ-proteobacteria,23 strains), 5 strains of Bacteroidetes (Sphingobacteria,2 strains; Flavobacteria 3 strains), 5 strains of Actinobacteria and 8 strains of Firmicutes (Bacilli, 8 strains).5. Phe- degrading bacterium F2 formed the clear zones in MM2 and 2216E plates by the sublimate-plate method, and no clear zones were observed in other PAH-degrading bacteria. The different PAH-degrading bacteria had various growth ways to utilize PAHs as sole carbon source. In addition, bacterial degradation effects to PAHs were also studied by mixture of several PAH-degrading bacteria according to information from DGGE profiles. The results of degrading rates by HPLC showed that either Phe-degrading bacteria or mixture of PAH-degrading bacteria had the stronger degradation ability to phenanthrene. The degradation rates to the three rings of PAHs were higher than those of the four or five rings of PAHs.
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