title: A Comparison of Microbial Water Quality and Diversity for Ballast and Tropical Harbor Waters.
abstract: Indicator organisms and antibiotic resistance were used as a proxy to measure microbial water quality of ballast tanks of ships, and surface waters in a tropical harbor. The survival of marine bacteria in ballast tanks appeared to diminish over longer water retention time, with a reduction of cell viability observed after a week based on heterotrophic plate counts. Pyrosequencing of 16S rRNA genes showed distinct differences in microbial composition of ballast and harbor waters. The harbor waters had a higher abundance of operational taxonomic units (OTUs) assigned to Cyanobacteria (Synechococcus spp.) and α-proteobacteria (SAR11 members), while marine hydrocarbon degraders such as γ-proteobacteria (Ocenspirillaes spp., Thiotrchales spp.) and Bacteroidetes (Flavobacteriales spp.) dominated the ballast water samples. Screening of indicator organisms found Escherichia coli (E. coli), Enterococcus and Pseudomonas aeruginosa (P. aeruginosa) in two or more of the ballast and harbor water samples tested. Vibrio spp. and Salmonella spp. were detected exclusively in harbor water samples. Using quantitative PCR (qPCR), we screened for 13 antibiotic resistant gene (ARG) targets and found higher abundances of sul1 (4.13-3.44 x 102 copies/mL), dfrA (0.77-1.80 x10 copies/mL) and cfr (2.00-5.21 copies/mL) genes compared to the other ARG targets selected for this survey. These genes encode for resistance to sulfonamides, trimethoprim and chloramphenicol-florfenicol antibiotics, which are also known to persist in sediments of aquaculture farms and coastal environments. Among the ARGs screened, we found significant correlations (P<0.05) between ereA, ermG, cfr and tetO genes to one or more of the indicator organisms detected in this study, which may suggest that these members contribute to the environmental resistome. This study provides a baseline water quality survey, quantitatively assessing indicators of antibiotic resistance, potentially pathogenic organisms and a broad-brush description of difference in microbial composition and diversity between open oceans and tropical coastal environments through the use of next generation sequencing technology.
authors.affiliation: National University of Singapore, Department of Civil and Environmental Engineering, Singapore, Singapore.
authors.forename: Charmaine
authors.initials: C
authors.lastname: Ng
authors.affiliation: National University of Singapore, Department of Civil and Environmental Engineering, Singapore, Singapore.
authors.forename: Thai-Hoang
authors.initials: TH
authors.lastname: Le
authors.affiliation: National University of Singapore, Department of Civil and Environmental Engineering, Singapore, Singapore.
authors.forename: Shin Giek
authors.initials: SG
authors.lastname: Goh
authors.affiliation: National University of Singapore, Department of Civil and Environmental Engineering, Singapore, Singapore.
authors.forename: Liang
authors.initials: L
authors.lastname: Liang
authors.affiliation: Michigan State University, Department of Microbiology and Molecular Genetics, East Lansing, Michigan, United States of America.
authors.forename: Yiseul
authors.initials: Y
authors.lastname: Kim
authors.affiliation: Michigan State University, Department of Microbiology and Molecular Genetics, East Lansing, Michigan, United States of America.
authors.forename: Joan B
authors.initials: JB
authors.lastname: Rose
authors.affiliation: National University of Singapore, Department of Civil and Environmental Engineering, Singapore, Singapore.|National University of Singapore Environmental Research Institute (NERI), Singapore, Singapore.
authors.forename: Karina Gin
authors.initials: KG
authors.lastname: Yew-Hoong
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D002701:Chloramphenicol / Q000494:pharmacology; D016000:Cluster Analysis; D004352:Drug Resistance, Microbial; D016983:Enterococcus / Q000187:drug effects / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D059014:High-Throughput Nucleotide Sequencing; D025341:Principal Component Analysis; D012336:RNA, Ribosomal, 16S / Q000032:analysis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012475:Salmonella / Q000235:genetics; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013449:Sulfonamides / Q000494:pharmacology; D014295:Trimethoprim / Q000494:pharmacology; D014733:Vibrio / Q000235:genetics; D060753:Water Quality
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D012336:RNA, Ribosomal, 16S; D013449:Sulfonamides; D002701:Chloramphenicol; D014295:Trimethoprim