Specificity and longevity of a bacterial interspecies mutual cooperation benefiting organic micropollutant biodegradation

Aminobacter niigataensis MSH1 is a candidate for bioaugmentation of sand filters in drinking water treatment plants (DWTP), as it mineralizes the ubiquitous groundwater micropollutant 2,6-dichlorobenzamide (BAM). The DWTP sand filter isolate Piscinibacter sp. K169 improves BAM mineralization by MSH1 in an apparent accidental mutual cooperation, and co-inoculation of the organism was proposed to assist bioaugmentation with MSH1. In this study, we questioned whether this accidental mutual positive interaction extends to four other pesticide catabolic bacterial strains of the same or a different genus of MSH1, and examined the longevity of the cooperation. Negative interactions were never observed in either direction. As observed for BAM mineralization by MSH1, K169 stimulated BAM mineralization by A. niigataensis LG1 and 2,4-D mineralization by Cupriavidus pinatubonensis JMP134 without affecting the cell density of the catabolic strains. Linuron mineralization by Variovorax sp. SRS16 and carbofuran mineralization by Novosphingobium sp. KN65.2 were not affected. In the other direction, growth of K169 was stimulated by all pesticide catabolic strains except JMP134, indicating a common underlying mechanism. After 2 weeks, the beneficial effects of K169 on MSH1, LG1, and JMP134 functionality diminished or even reversed, likely because of organic carbon depletion. In contrast, cell densities of K169 in all dual-species systems remained higher than in the K169 monoculture system. This study extends our knowledge on accidental interactions and the beneficial effect of a sand filter isolate toward other pesticide degraders, opening doors for Piscinibacter sp. K169-assisted bioaugmentation of other/multiple pesticide degraders in DWTPs.

IMPORTANCE

Sand‑filter bioaugmentation with the BAM‑catabolic Aminobacter niigataensis MSH1 represents an advanced strategy for removing BAM from groundwater in drinking water treatment; however, prior studies indicate that efficacy lasts only for 1–2 weeks. Piscinibacter sp. K169, an isolate from drinking‑water sand filters, supports mineralization of BAM by MSH1 through accidental mutual cooperation, and co‑inoculation with K169 was suggested as an innovation to improve MSH1 bioaugmentation. We show that K169 promotes mineralization of OMPs by other bacteria and, hence, that the K169-degrader cooperation can be extended to support removal of other or even multiple OMPs. Benefits declined over time, likely due to nutrient depletion, making nutrient management a requirement for maintaining the cooperation. To the best of our knowledge, this is the first study to examine specificity in accidental microbial cooperation, especially in a bioaugmentation context of water treatment. It is relevant both to a fundamental understanding of accidental microbial interactions and to applications in water treatment.