Biyofilmde sülfat indirgeyen anaerop bakteriler

Anaerop sülfat indirgeyen bakteriler (SRB), insan barsak sisteminde oluşan biyofilm tabakası içinde yaşayabilmekte ve kükürt bileşiklerini sitotoksik bir ürün olan hidrojen sülfüre (H2S) indirgemektedirler. H2S, insanlarda ülseratif kolite neden olurken, SRB septisemiye ve karaciğer absesine yol açmaktadırlar. H2S 'e ek olarak, SRB 'in ürettiği ekstraselüler polimerik maddelerden O-antijeni, genetik olarak yatkın bireylerde immün yanıta neden olabilmekte ve ülseratif kolitin karakteristik özelliği olan iltihaplanma sürecini başlatabilmektedir. Su deposu malzemesi olarak çoğunlukla galvaniz çelik kullanılmaktadır ve su depoları mikroorganizmaların özellikle de SRB'in üremesine uygun ortamlara sahiptir. Bu çalışmada SRB'in galvanizli çelik üzerinde biyofılm oluşturabilme ve varlıklarını sürdürebilme yetenekleri incelenmiştir. Taramalı elektron mikroskobu (SEM) mikrografı ile SRB'in galvanizli çelik yüzeye tutunabildikleri ve kolonize olabildikleri gösterilmiştir. Hem kültürdeki (planktonik) hem de biyofilmdeki (sessil) SRB, maksimum sayıya 72. saatte ulaşmışlar ve sırasıyla 9.6 hücre/mi ve 8.04 hücre/cm olarak saptanmışlardır.

Sulphate reducing anaerobic bacteria in biofilm

Anaerobic sulphate reducing bacteria (SRB) can live in biofilm layer formed within the human gastrointestinal system and reduce sulfur compounds to hydrogen sulfide (H2S) that is a cytotoxic product. While H2S causes ulcerative colitis in human, SRB trigger liver abscess and septicemia. In addition to the effect of H2S, extracellular polymeric substances produced by SRB may contain highly immunogenic O-antigen. Such antigens may cause an immune response in genetically predisposed individuals and initiate to the inflammatory process characteristic of ulcerative colitis. Galvanized steel is frequently used in construction of water containers which have good conditions for growing of microorganisms especially SRB. In this study we investigated SRB's abilities of biofilm formation and surviving on surfaces of galvanized steel. SEM shows that SRB could attach to galvanized steel surface and colonize on the surface. The cell concentrations ofplanktonic and sessile SRB increased to a maximum of 9.6 cells/ml and 8.04 cells/cm2 after 72 hours of incubation, respectively.

Kaynakça

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