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Impact of 4-chlorophenol contamination and/or inoculation with the 4-chlorophenol-degrading strain, Arthrobacter chlorophenolicus A6L, on soil bacterial community structure
Södertörn University, Avdelning Naturvetenskap. Karolinska Institutet.
Södertörn University, Avdelning Naturvetenskap.
2002 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 42, no 3, 387-97 p.Article in journal (Refereed) Published
Abstract [en]

The 4-chlorophenol-degrading strain, Arthrobacter chlorophenolicus A6L (chromosomally tagged with the firefly luciferase gene, luc) was inoculated into 4-chlorophenol-contaminated soil to assess the impact of bioaugmentation with a biodegrading strain on the indigenous microbiota. Simultaneously, the impact of 4-chlorophenol alone, or inoculation with A. chlorophenolicus into non-contaminated soil, was addressed. Using terminal restriction fragment length polymorphism (T-RFLP) several significant changes were detected in community fingerprint patterns obtained from soil microcosms treated under the different conditions. The relative abundances of some populations, as judged by the relative intensity of terminal restriction fragments, were significantly impacted by either 4-chlorophenol, A. chlorophenolicus inoculation, or by a combination of both inoculation and 4-chlorophenol contamination. Some populations were significantly stimulated and others were significantly repressed when compared to control soil with no additions. For several peaks, the positive or negative impact imposed by the treatments increased over the 13-day incubation period. Some members of the bacterial community were specifically sensitive to A. chlorophenolicus inoculation or to 4-chlorophenol contamination, whereas other populations remained relatively unaffected by any of the treatments. The A. chlorophenolicus inoculum was also monitored by T-RFLP and was found to have a significantly higher relative abundance in soil contaminated with 4-chlorophenol. These results were substantiated by a high correlation to luciferase activity measurements and the number of colony forming units of the inoculum. Therefore, the A. chlorophenolicus A6L population was positively stimulated by the presence of the 4-chlorophenol substrate (180 microg g(-1) soil) that it catabolized during the first 8 days of the incubation period as a carbon and energy source. Together, these results demonstrate that specific populations in the soil bacterial community rapidly fluctuated in response to specific disturbances and the resulting shifts in the community may therefore represent an adjustment in community structure favoring those populations best capable of responding to novel stress scenarios.

Place, publisher, year, edition, pages
2002. Vol. 42, no 3, 387-97 p.
National Category
URN: urn:nbn:se:sh:diva-17639DOI: 10.1111/j.1574-6941.2002.tb01028.xISI: 000179545100007PubMedID: 19709298ScopusID: 2-s2.0-0036890005OAI: diva2:577060
Available from: 2012-12-14 Created: 2012-12-14 Last updated: 2017-02-08Bibliographically approved
In thesis
1. Use of microbiomics to study human impacts on complex microbial communities
Open this publication in new window or tab >>Use of microbiomics to study human impacts on complex microbial communities
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study of bacterial communities in nature is currently a challenge. The majority of bacteria in clinical and environmental samples have not yet been cultured and therefore we cannot fully understand their roles in nature and how the ecological balance in a specific microbial ecosystem can be disrupted. For example, exposure to pollutants in soil and antibiotics in the human gut can have large consequences on microbial populations but the magnitude of these impacts is difficult to assess. In this thesis, a combination of molecular techniques, microbiomics, were used to assess complex microbial communities in soil and the human gut. One goal of this thesis was to study the impact of the toxic compound, 4-chlorophenol, on the soil microbiota. In addition, a specific 4-chlorophenol degrading bacterium, Arthrobacter chlorophenolicus, was monitored in soil. In order to monitor the cells they were chromosomally tagged with marker genes encoding either the green fluorescent protein (the gfp gene) or firefly luciferase (the luc gene). During degradation of high levels of 4-chlorophenol in soil, total cells counts of A. chlorophenolicus cells could be measured by flow cytometry (GFP protein) and the metabolic activity could be measured by lurninometry (luciferase activity). In addition, the relative abundance of A. chlorophenolicus in soil could be measured by terminal restriction fragment length polymorphism (T-RFLP) and a higher relative abundance was detected in soil contaminated with 4chlorophenol compared with non-treated soil. The impacts of 4-chlorophenol and A. chlorophenolicus on the dominant members of the soil microbiota were also assessed by T-RFLP. Another goal of this thesis was to study the impact of a short term antibiotic administration in a long term perspective, using either clindamycin, in a two year study or a triple therapy for eradication of Helicobacter pylori containing clarithromycin and metronidazole, in a four year study, on the human fecal microbiota. Both the total bacterial community and specific populations, i.e. Bacteroides spp. and Enterococcus spp., were monitored by T-RFLP. The Bacteroides populations never returned to their pre-treatment composition after clindamycin exposure during the two year study period. Selection and persistence of resistant Bacteroides clones up to two years after treatment was furthermore detected. In the four year study, Enterococcus populations increased as a response to the clarithromycin and metronidazole treatment. An increase in the levels of antibiotic resistance genes, specific erm genes, conferring resistance to macrolides and lincosamides were detected for up to 2 and 4 years after both types of antibiotic treatments in the respective studies. It was also possible to specifically monitor two probiotic Lactobacillus strains and their transient colonization by T-RFLP. In conclusion, the use of a polyphasic approach with complementary analytical tools made it possible to obtain a comprehensive picture of complex microbial communities. In addition, specific bacteria of interest in complex soil and fecal samples could be monitored using microbiomics approaches.

Place, publisher, year, edition, pages
Stockholm: Karolinska instiutet, 2006. 37 p.
National Category
Biological Sciences
urn:nbn:se:sh:diva-31990 (URN)91-7140-960-2 (ISBN)
Public defence
2006-12-15, MB416, Alfred Nobels allé 7, Huddinge, 10:00 (English)
Available from: 2017-02-08 Created: 2017-02-08 Last updated: 2017-02-08Bibliographically approved

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