Isolation and Molecular Characterization of Biofouling Bacteria and Profiling of Quorum Sensing Signal Molecules from Membrane Bioreactor Activated Sludge

Abstract

The formation of biofilm in a membrane bioreactor depends on the production of various signaling molecules like N-acyl homoserine lactones (AHLs). In the present study, a total of 200 bacterial strains were isolated from membrane bioreactor activated sludge and screened for AHLs production using two biosensor systems, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136. A correlation between AHLs production and biofilm formation has been made among screened AHLs producing strains. The 16S rRNA gene sequence analysis revealed the dominance of Aeromonas and Enterobacter sp. in AHLs production; however few a species of Serratia, Leclercia, Pseudomonas, Klebsiella, Raoultella and Citrobacter were also identified. The chromatographic characterization of sludge extract showed the presence of a broad range of quorum sensing signal molecules. Further identification of sludge AHLs by thin layer chromatography bioassay and high performance liquid chromatography confirms the presence of C4-HSL, C6-HSL, C8-HSL, 3-oxo-C8-HSL, C10-HSL, C12-HSL, 3-oxo-C12-HSL and C14-HSL. The occurrence of AHLs in sludge extract and dominance of Aeromonas and Enterobacter sp. in activated sludge suggests the key role of these bacterial strains in AHLs production and thereby membrane fouling.

Quorum Sensing Interference and Structural Variation of Quorum Sensing Mimics in Australian Soft Coral

“…The genera of all the bacteria isolated, regardless of activity detected in this study, have previously been reported to possess or interact with QS systems (Ansaldi et al, 2002;Long et al, 2003;Waters and Bassler, 2005;Case et al, 2008;Tait et al, 2009Tait et al, , 2010Nithya et al, 2010;Albuquerque and Casadevall, 2012;Lade et al, 2014), providing support for the hypothesis that QS is one of the mechanisms regulating coral associated microbial communities.…”

Microbial population dynamics and profiling of quorum sensing agents in membrane bioreactor

“…5b). Quantification of biofilm, at different time intervals, confirms that all the strains seem to have different biofilm forming tendencies, irrespective of the growth rate (Lade et al, 2014). Hence, it may be concluded that the rate of biofilm formation does not always depend on the bacterial growth, rather there are some other agents (or chemical signals) responsible for gauging population density.…”

“…Hence, the presence of these species may verify the better nitrification (Waheed et al, 2013). All the reported species and their role in overall treatment performance have also been discussed by Chong et al (2012) and Lade et al (2014).…”

“…Bioassay, consisting of an indicating agar plate and bacteria to be tested, was carried out as per method described by Lade et al (2014). A fresh culture, of CV026 or A136 and LB agar were mixed in a ratio of 1:9 to prepare indicating agar plate.…”

“…Plates were sealed with para film and incubated at 28 C for 24, 48 and 72 h under static condition. A classical crystal violet assay was used to quantify the biofilm (Lade et al, 2014). Amount of crystal violet absorbed by biofilm was extracted with 200 ml ethanol (95%), per well for 1 h, (18) and OD 595nm was measured with a UVeVis spectrophotometer.…”