Ecological insights into the underlying evolutionary patterns of biofilm formation from biological wastewater treatment systems: Red or Black Queen Hypothesis?

Abstract

Interspecies interactions and phylogenetic distances were studied to reveal the underlying evolutionary adaptations of biofilms sourced from wastewater treatment processes. Based on 380 pairwise cocultures of 40 strains from two microbial aggregates (surface‐attached and mobile aggregates [flocs]) at two substrate concentrations (LB broth and 0.1× LB broth), interspecies interactions were explored using biofilm classification schemes. There was a strong source‐dependence of biofilm development formed by the monocultures, that is, a higher biofilm formation potential for strains from attached aggregates than for those from sludge flocs at both substrate concentrations. Interestingly, the results showed that total biofilm reduction was dominant in the dual‐species biofilm sourced from flocs in both LB broth (67.37%) and 0.1× LB broth (64.21%), indicating high interspecific competition in mobile aggregates and the independence of substrate concentrations. However, biofilm reduction was higher (33.68%) than induction (19.37%) for the biofilms formed by surface‐attached aggregates in LB broth, while the opposite trend was apparent in 0.1× LB broth, suggesting the occurrence of indeterministic processes for biofilm formation and important roles of substrate concentrations. In addition, the more closely related phylogenetic relationships of cocultures from mobile aggregates were consistent with higher competition compared with those from surface‐attached aggregates. Overall, the underlying evolutionary patterns of biofilms formed from mobile aggregates consistently followed the essence of the “Red Queen Hypothesis,” while biofilms developed from surface‐attached aggregates were not deterministic. This study advanced our understanding of biofilm‐related treatment processes using the principles of microbial ecology.

Climatic Alterations Influence Bacterial Growth, Biofilm Production and Antimicrobial Resistance Profiles in Aeromonas spp.

“…If the combined temperature and pH conditions fall within the optimal range for multiplication and virulence expression for each isolate, they will dictate the isolate’s competitiveness and ability to survive in an environment composed of multiple species [ 26 , 27 ]. Further, the level of interspecific competition for the limited resources will also hinder each isolate’s ability to allocate nutrients to processes such as biofilm production, contrary to what occurs in pure cultures [ 28 ]. Finally, environmental oscillations of abiotic factors, such as temperature, will create additional disturbances for the bacterial communities [ 22 ] and the overall combination of external stressors with internal competition is likely to impact the final biofilm production.…”

New Methods, New Concepts: What Can Be Applied to Freshwater Periphyton?

“…For example, studies on cell cultures of the brown alga Ectocarpus had shown that presence of specific associated bacteria increase the tolerance of the algal host to low salinity (Dittami et al, 2016). Besides synergistic interactions, a multispecies community inevitably faces competitive antagonistic interactions among species (Freilich et al, 2011;Allen et al, 2015;Yuan and Meng, 2020). Last, studies have shown that in the absence of carbon limitation, heterotrophs can out-compete algae for nutrients and thus suppress algal growth (Wyatt et al, 2019).…”

“…Models suggest that within these communities deletions might often occur in a complementary fashion among various interacting bacteria (Morris et al, 2012;Sachs and Hollowell, 2012). Yuan and Meng (2020) modeled the development of biofilms in a bioreactor and provided an overview of prevailing interactions. They found a difference in interactions in mobile (flocks) vs. those in surface-attached biofilms.…”

“…In surface-attached biofilms, however, the relationships were less competitive and more cooperative. However, as the authors note themselves, their experiment had lasted for a too short time to demonstrate the ecological effects of possible loss-of-function mutations (Yuan and Meng, 2020).…”

“…When taking into account chemical signaling and chemotactic motility, the advantage can be shifted more to the side of non-producers and co-existing one-producers ( Stump et al, 2018 ). However, in the case of biofilms and algal-bacterial interactions, microbial communities face selection according to substrate type and ability to co-exist with a specific algal host and other microbes ( Goecke et al, 2013 ; Stock et al, 2019 ; Yuan and Meng, 2020 ). This decreased effect of neighbor uncertainty can result in strengthening mutualistic relationships via the BQH.…”