Re ECF Project: 2012-30

Project Title: Exploring Microbial Diversity and Antibiotic Resistant Genes of Hong Kong Marine Sediment using Advanced Molecular Techniques

Applicant: Dr. Zhang Tong, Department of Civil Engineering, The University of Hong Kong

Total Approved Grant: $494,760

Duration: 1/3/2014 to 30/6/2015

Project Status/Remarks: Completed

This project aims to investigate microbial diversity and antibiotic resistant genes in Hong Kong marine sediment. The three main objectives of the project are to:

  1. comprehensively investigate the bacterial diversity in marine sediment samples which were collected from 35 locations across Hong Kong coastal waters during the summer of 2012 (following the same sampling locations adopted by the Environmental Protection Department);
  2. determine antibiotics resistance genes (ARGs) in the sediment samples and hence provide a thorough evaluation on the antibiotics contamination in the marine environment of Hong Kong; and
  3. study the relationships between the diversity of microorganisms with that of macroinfunal organisms in local sediments and with the sediment quality data obtained by EPD.

Summary of the Findings/Outcomes:
In general, the diversities of bacterial communities in most of the 35 Hong Kong sediments were high, although much lower diversities were detected in several stations from the Tolo Harbour. The major bacterial divisions or subdivisions were Deltaproteobacteria, Gammaproteobacteria, Firmicutes, Chloroflexi, Acidobacteria, etc. The result also indicated a location-independent pattern for the bacterial community. Sulfate reducing prokaryotes (SRPs) were dominant microbes in sediments. It showed that relative abundances of major sulfate reducing prokaryote genera to total prokaryotes were consistently lower in the more seriously polluted sediments, indicating that the relative abundance of SRPs was a negatively correlated biomarker for evaluating human impacts. However, a uni-model distribution pattern for SRPs along with the pollution gradient was observed. The dominant antibiotics in the sampled Hong Kong sediments were roxithromycin, sulfadiazine and sulfamethoxazole. Although total antibiotics resistance genes (ARGs) were enriched in sediments from the polluted sites with high chemical oxygen demand, distribution of single major ARG types could be explained neither by individual sediment parameters nor the corresponding antibiotics concentrations. It supported the hypothesis that the persistence of ARGs in sediments might not need the selection of antibiotics. Generally, no significant correlation between the biodiversity of bacterial community and macroinfauna was found. Two pairs of co-occurrence between benthic animals and microbes were observed in significantly positive correlation. It suggested the environmental co-selection for microbes and animals or potential direct interactions between the two types of organisms.