Plasmid-mediated bioaugmentation of activated sludge bacteria in a sequencing batch moving bed reactor using pNB2

Abstract

Aims: The applicability of plasmid pNB2 for bioaugmentation of bacteria in model wastewater treatment reactors receiving 3‐chloroaniline (3‐CA) was investigated. Methods and Results: A setup of three biofilm reactors was studied, all initially inoculated with bacteria from activated sludge. Reactor PB received a Pseudomonas putida pNB2 donor strain not able to degrade 3‐CA. Positive control reactor P received a 3‐CA degrading Comamonas testosteroni pNB2‐transconjugant. The negative control reactor N remained unchanged. Reactor P showed 3‐CA degradation from the beginning of the experiment whereas in reactor PB, degradation started after an initial lag period. No degradation was observed in reactor N. PCR analysis showed that the P. putida donor abundance dropped in reactor PB, whereas the plasmid abundance did not, indicating transfer to other bacteria. A number of different 3‐CA degrading C. testosteroni strains carrying pNB2 could be isolated from reactor PB. Conclusions: A successful plasmid‐mediated bioaugmentation was achieved with C. testosteroni being the dominant 3‐CA degrading pNB2 transconjugant species active in reactor PB. Significance and Impact of the Study: The study underlines the potential of gene transfer to contribute to establishment and spread of genetic information in general, particularly emphasizing the spread of xenobiotic degrading potential by dissemination of catabolic genes.

The Behavior and Significance of Degradative Plasmids Belonging to Inc Groups in <i>Pseudomonas</i> within Natural Environments and Microcosms

“…pNB2 is another IncP-1 plasmid that carries some of the genes required for 3-chloroaniline's degradation (12), although its complete nucleotide sequence has not yet been determined. This plasmid is also transferable to indigenous bacteria, and the transconjugants detected principally belonged to the family Comamonadaceae within the β-Proteobacteria, in activated sludge or biofilm reactors, in contrast to pJP4 (4,7,8). Some γ-Proteobacteria are not able to express 3-chloroaniline-degradative enzymes efficiently (4; 7, 36), resulting in biases in the spectra of transconjugants.…”

“…Adequate dispersion of biodegradative microorganisms over contaminated areas is also problematic. To overcome these problems, 'gene bioaugmentation' or 'plasmid-mediated bioaugmentation' (4,7,23,82), the introduction of appropriate degradative plasmids contained within a microbial host, has been attempted. The rationale for this approach is that the degradative genes survive through incorporation into indigenous bacteria by horizontal transfer.…”

Bioremediation: Plasmid-Mediated Bioaugmentation of Microbial Communities – Experience from Laboratory-Scale Bioreactors

“…The authors in that particular study attributed the rapid decline in denitrifying microorganisms to grazing by higher-order protozoan ciliates. On the other hand, bioaugmentation via in situ genetic manipulation (the introduction of catabolic genes into an existing indigenous community by means of HGT via conjugation or transformation) may result in a lasting presence of the introduced degradative genes in an existing microbial community (Bathe, 2004;Bathe et al, 2004bBathe et al, , 2005Bathe et al, , 2009. In this manner, catabolic enzymes encoded by genes on mobile genetic elements carried by an appropriate bacterial host are introduced to indigenous populations ( Figure 1).…”

Crude Oil Metagenomics for Better Bioremediation of Contaminated Environments

“…Certain studies, moreover, established the possibility of improving the effectiveness of the bioremediation by the directly addition of the genes of interest in the polluted ecosystems. In this case, gene transfers between donor bacteria of catabolic plasmid and the endogenous populations allow the biological degradation of pollutants (Bathe et al, 2005). The addition of microorganisms in the environment is not frequently practiced because it is always difficult to control (Van Veen et al, 1997).…”