title: Method for assessment of viability and morphological changes of bacteria in the early stage of colony formation on a simulated natural environment.
abstract: A quantitative analysis of changes in the physiological status of bacterial cells is a fundamental type of study in microbiological research. We devised a method for measuring the viability of bacteria in the early stage of colony formation on a simulated natural environment. In this method, a solid medium containing soil extract was used, and the formation of bacterial microcolonies on a membrane filter was determined by use of a laser scanning cytometer combined with live-dead fluorescent dyes. A polychlorinated biphenyl degrader, Comamonas testosteroni TK102, was used in this study. Surprisingly, approximately 20% of the microcolonies had their growth stopped and eventually died. In the presence of biphenyl, the growth arrest was increased to 50%, and filamentous cells were observed in the colonies. Predicted intermediate metabolites of biphenyl were added to the medium to determine the relationship between the change of viability and the production of metabolites, and the addition of 2,3-dihydroxybiphenyl showed low viability. The arrest was not observed to occur on nutrient-rich medium, suggesting that the change in viability might occur in a nutrient-poor natural condition. The results of this study demonstrated that toxic metabolites of xenobiotics might change cell viability in the natural environment.
authors.affiliation: Department of Built Environment, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Shimomura
authors.forename: Ryuzo
authors.initials: R
authors.lastname: Ohno
authors.forename: Fusako
authors.initials: F
authors.lastname: Kawai
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Kimbara
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure*; D001431:Bacteriological Techniques; D001673:Biodegradation, Environmental; D001713:Biphenyl Compounds / Q000378:metabolism* / Q000494:pharmacology; D003470:Culture Media; D005659:Fungicides, Industrial / Q000378:metabolism* / Q000494:pharmacology; D047569:Laser Scanning Cytometry / Q000295:instrumentation / Q000379:methods*; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology
chemical_list: D001713:Biphenyl Compounds; D003470:Culture Media; D005659:Fungicides, Industrial; D012987:Soil; C010574:biphenyl