Nitrosomonas europaea biofilm formation is enhanced by Pseudomonas aeruginosa

Abstract

Biofilms are useful in biotechnology applications such as wastewater treatment, where aggregation of cells on surfaces can increase retention of slow-growing organisms such as ammonia-oxidizing bacteria (AOB). The formation and morphological development of polymicrobial biofilms including AOB are not thoroughly understood. Here, we investigated the formation of Nitrosomonas europaea AOB biofilms in flow cell systems. Nitrosomonas europaea developed substantially greater biovolume in co-culture with heterotrophic Pseudomonas aeruginosa than when cultured alone. In single-species biofilms, N. europaea formed thin, dispersed layers of cells. Contrastingly, when N. europaea was added to flow cells containing pre-established P. aeruginosa biofilms, N. europaea associated closely with P. aeruginosa, resulting in dual-species clusters with greater quantities of N. europaea. These results indicate that P. aeruginosa enhances the formation of N. europaea in biofilms. This favorable association of N. europaea with heterotrophic biofilms is expected to facilitate development of improved strategies for retention of N. europaea and other slow-growing AOB in engineered bioreactors.

Quantification and Phylogenetic Analysis of Ammonia Oxidizers on Biofilm Carriers in a Full-Scale Wastewater Treatment Plant

“…The organisms of this lineage have been found in biofilms in other wastewater treatment systems (Egli et al, 2003;Okabe et al, 2004;Satoh et al, 2006). Moreover, several isolates of this lineage are known to form biofilms with other heterotrophic bacteria (Tsuneda et al, 2001;Petrovich et al, 2017). AOB, which has the ability to form biofilms, may accumulate on BC.…”

Nitrite production by ammonia‐oxidizing bacteria mediates chloramine decay and resistance in a mixed‐species community

“…Accordingly, this study expands upon a previously published model using a mixed-species nitrifying community containing N. europaea and heterotrophic bacteria which varied in community composition in response to growth and culture ª 2020 The Authors. Microbial Biotechnology published by Society for Applied Microbiology and John Wiley & Sons Ltd, Microbial Biotechnology, 13, 1847-1859 conditions (Petrovich et al, 2017;Keshvardoust et al, 2019), to explore the potential contributions of AOB to biofilms and chloramine decay. This experimental microbial community was comprised of nearly 50% Nitrosomonasaceae (AOBs) and approximately 50% of heterotrophic bacteria when grown in nitrification medium.…”

“…Nitrite produced during nitritation can be readily and directly oxidized by chloramine, resulting in the formation of nitrate and the decomposition of chloramine into ammonia and free chloride (Vikesland et al ., 2001). Thus, the organic carbon and energy derived from the oxidation of ammonia produced via the decomposition of chloramine can be coupled with the reduction in chloramine concentration to allow for the proliferation of both nitrifying bacteria and heterotrophic microorganisms in surface‐attached mixed‐species biofilms (Petrovich et al ., 2017; Keshvardoust et al ., 2019).…”

“…To improve our understanding of the mechanisms of chloramine decay and microbial resistance to chloramination, a microbial model that addresses the ecological role of nitrifying and non‐nitrifying organisms, such as those found in chloramine‐treated drinking water systems will be invaluable to complement the chemical approaches that have been well‐studied. In this study, Pseudomonas aeruginosa was used to model a heterotrophic bacterium, while a mixed‐species community containing N. europaea and other bacteria was used to model mixed‐species nitrifying communities (Petrovich et al ., 2017; Keshvardoust et al ., 2019). Pseudomonas aeruginosa is a model biofilm‐forming organism that produces high amounts of alginate (Ochsner and Reiser, 1995; Whiteley et al ., 2001; Drenkard and Ausubel, 2002; Bazire et al ., 2005; Barraud et al ., 2006), that is known to associate with other organisms in mixed‐species biofilms (Riedel et al ., 2001) and can be found in drinking water (Shrivastava et al ., 2004).…”

“…Although other species, such as Nitrosomonas oligotropha , have been suggested to have a greater affinity for ammonia in weakly chloraminated waters and greater involvement in chloramine decay than N. europaea (Regan et al ., 2002; Regan et al ., 2003; Krishna et al ., 2013), N. europaea possesses the same ammonia oxidation pathway and has been more thoroughly investigated (Zhang et al ., 2009), under a range of diverse conditions reflecting environments from soil (Blackmer et al ., 1980) to drinking water (Maestre et al ., 2013). Accordingly, this study expands upon a previously published model using a mixed‐species nitrifying community containing N. europaea and heterotrophic bacteria which varied in community composition in response to growth and culture conditions (Petrovich et al ., 2017; Keshvardoust et al ., 2019), to explore the potential contributions of AOB to biofilms and chloramine decay. This experimental microbial community was comprised of nearly 50% Nitrosomonasaceae (AOBs) and approximately 50% of heterotrophic bacteria when grown in nitrification medium.…”