On the other hand, the study of the P. fluorescens strain's ability to produce a biofilm on contaminated PCP medium showed that the addition of the xenobiotic PCP in the growth medium at an increasing rate enhances the biofilm formation capacity. Meliani & Bensoltane (2014) reported that the P. fluorescens and P. aeruginosa isolates develop an important biofilm mass development, to protect cells from hostile environments. Therefore, the biofilm lifestyle can protect microorganisms against the host immune system and harmful environmental conditions. This protection enables microorganisms to survive and prosper (Anderson & Toole 2008). So, biofilm formation and development played an important role in the bioremediation of some waste contaminated sites (Del Castillo et al. 2012). Biofilm reactors or devices are very interesting for the remediation of xenobiotic compounds (Das et al. 2012). Thus, environmental stress conditions could affect biofilm production (Poole 2012), since biofilm development is considered as a natural strategy to maintain a favorable niche in stressful and unfriendly environments (Meliani & Bensoltane 2014). A number of studies suggested a close relationship between hydrocarbon degradation and biofilm formation (Dasgupta et al. 2013). Previous investigations have shown that the degradation of environmental pollutants is more efficient by microorganisms in biofilms than by free-living bacteria (Singh & Walker 2006; Verhagen et al. 2011). As an example, P. stutzeri biofilm-associated cells successfully degraded naphthalene and survived in petroleum contaminated soil, although biofilm cultures could degrade the pesticide chloropropham slower than planktonic cultures, and could not produce intermediate toxic compounds (Verhagen et al. 2011). The biofilm systems were efficient in removing toxic trace compounds in wastewater, according to various electrostatic and hydrophobic interactions and adsorption/desorption phenomena.
bergey's manual of systematic bacteriology free ebook 643
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