Aminobacter sp. MSH1 invades sand filter community biofilms while retaining 2,6-dichlorobenzamide degradation functionality under C and N limiting conditions

Abstract

Aminobacter sp. MSH1 is of interest for bioaugmentation of biofiltration units in drinking water treatment plants (DWTPs) due to its ability to degrade the groundwater micropollutant 2,6-dichlorobenzamide (BAM). Using a continuous flow chamber biofilm model, MSH1 was previously shown to colonize surfaces and degrade BAM at trace concentrations as low as 1 μg/L under the oligotrophic conditions found in DWTPs. In DWTP filtration units, MSH1 has to compete with the resident biofilm microbiota for space and nutrients. Using the same model, we examined how a sand filter community (SFC) affects MSH1's BAM-degrading activity and biofilm formation under C- and N-limiting conditions when fed with trace concentrations of BAM. MSH1 was inoculated simultaneously with the SFC (co-colonization mode) or after the SFC formed a biofilm (invasion mode). MSH1 successfully established in the SFC biofilm showing growth and activity. In co-colonization mode, MSH1 decreased in number in the presence of the SFC and formed isolated colonies, while specific BAM-degradation activity increased. In the invasion mode, MSH1 also decreased in numbers in the presence of the SFC but formed mixed colonies, while specific BAM degradation was unaffected. Our results show that MSH1 invades and performs successfully in an SFC biofilm under the oligotrophic conditions of DWTPs.

Individual-Based Modelling of Invasion in Bioaugmented Sand Filter Communities

“…In the former case, sufficient species are present in sufficient numbers to form the spiral patterns characteristic of this type of individual-based models, which have been shown to help maintain coexistence [40]. These patterns also qualitatively resemble those observed in in vitro experiments where a similar synthetic community of SFIs was co-cultured with MSH1 in the presence of BAM [18]. The spiral formations also enable spatial refuges, which have been observed to support species coexistence by allowing vulnerable species to persist at low but still significant levels [44].…”

“…These dynamics have also been observed for communities of microbial species [18] as well as for communities of higher organisms [45,46]. formation has commenced; this strain is the weakest in both competition structures.…”

“…We developed an IBM representing the in silico counterpart of this synthetic community, where competition structures were constructed based on pairwise competition outcomes, using data related to lag time λ and mineralization rate µ interaction effects in terms of mineralization performance. Our model was able to recover the qualitative dynamics observed in in vitro experiments with similar synthetic sand filter communities: the majority of the community collapsing to extinction and a subcommunity persisting [11,18]. The memberships of these subcommunities were consistent, and their presence could be explained based on their attributes as represented in the competition matrices.…”

“…Previous results with synthetic microbial communities with similar characteristics in terms of diversity and composition [18] and also for this particular synthetic community of MSH1 and 13 SFIs [11], highlighted the importance of the initial competition phase (before the addition of BAM) where all 13 SFIs are inoculated in the co-culture. Competition between the SFIs results in extinctions, leading to a stable subcommunity of reduced richness.…”

Bioaugmented Sand Filter Columns Provide Stable Removal of Pesticide Residue From Membrane Retentate

“…Indeed, we found that a large population of MSH1 was sustained in the sand filter columns throughout the present study despite the protozoan presence, enabling complete BAM removal as opposed to previous experiments (Albers et al, 2015b;Ellegaard-Jensen et al, 2016;Horemans et al, 2016) as mentioned above. Horemans et al (2017) found that MSH1 was able to successfully invade a sand filter community biofilm and achieve maximum 60% BAM removal under oligotrophic conditions. While the possible protective mechanism of our approach of allowing MSH1 to first form biofilm on the sand before exposing it to the indigenous microbiota remains to be determined through further studies, we provide some insight into possible interactions between the inoculated strain and the indigenous bacterial community colonizing the sand through sequencing of the prokaryotic biofilm community.…”