Predators and nutrient availability favor protozoa-resisting bacteria in aquatic systems

Abstract

The long co-existence of bacteria and protozoa has led to the development of bacterial protozoa resistance strategies, which are suggested to serve as drivers for the evolution of pathogenic bacteria. However, the ecological mechanisms underpinning selection for protozoa-resistance in aquatic bacteria are poorly known. To assess the role of nutrient availability and predation-pressure on selection for protozoa-resisting bacteria (PRB), an enrichment-dilution experiment was designed using laboratory microcosms containing natural lake water. PRB was monitored by screening 16S rRNA amplicon sequence data for reads assigned to bacteria that previously has been shown to resist degradation by amoebae. To estimate the effects of the microbial food web dynamics (microscopy of; heterotrophic bacteria, phytoplankton, protozoa and rotifers) and physicochemical variables on the PRB abundance in the study system, a joint species distribution modelling approach was used. The predation-pressure (ratio between predator and bacterial biomass) had a positive effect on the abundance of the PRB genus Mycobacterium, while perturbation (enrichment and dilution) favored the PRB genus Pseudomonas that dominated the bacterial community in the disturbed systems. Our results show that PRB with different ecological strategies can be expected in water of high and intermediate nutrient levels and after major disturbances of an aquatic system.

Non-Tuberculous Mycobacteria: Molecular and Physiological Bases of Virulence and Adaptation to Ecological Niches

“…Similarly to pathogenic mycobacteria and their ability to evade phagolysosomes and escape the lytic activity exerted by mammalian cells, namely the macrophages, NTM have the extraordinary ability to survive phagocytosis by protozoa such as amoebae and additionally grow as endosymbionts ( Figure 4 ) [ 154 , 155 , 156 , 157 , 158 ]. NTM are preferentially predated by protozoa since these microorganisms graze biofilms, the usual niche of NTM in both natural and engineered environments [ 154 , 155 , 156 , 157 , 158 ]. Several works have highlighted the association of free-living amoebae with mycobacteria, with M. leprae , M. avium , M. marinum , M. ulcerans , M. simiae , M. habane , M. gordonae , M kansasii , and M. xenopi revealing the capacity of intra-amoebal survival inside vacuoles [ 159 ].…”

“…The possibility to grow in endosymbiosis with protozoa protect NTM from extreme environmental conditions, namely the pressure exerted by natural antimicrobial compounds and starvation, especially due to NTM survival in encystment structures [ 154 , 155 , 156 , 157 , 158 ]. The persistence within amoeba has been related to the increase in the infectivity and virulence of M. avium and M. abscessus [ 167 ].…”

Protozoa populations are ecosystem engineers that shape prokaryotic community structure and function of the rumen microbial ecosystem

“…This is in line with the keystone predation model [23,38], which predicts that predation susceptible and resistant competitor species can coexist but negative selection by elevated predation in high productivity leads to stronger positive selection for predation resistant bacteria, where the competitive niche-opening is filled by the latter. Examples for species involved in such ecological trade-offs between competition and predation include several genera of the Gammaproteobacteria that were shown to be predation-resistant against diverse protists in aquatic environments [39,40]. It was further speculated that type III, IV and type VI secretion systems, which are commonly encoded in their genomes, may assist in the observed digestion resistance [39] with type III secretion system also identified in Gammaproteobacteria species in the rumen [41].…”

Effect of intermediate disturbance on soil microbial functional diversity depends on the amount of effective resources

“…Previous studies showing that excess P availability can relax microbial predator–prey relationships (which affects turnover), likely due to reduced demand for their cell contents enriched in P (nucleic acids, phospholipids, ribosomes, etc.) (Anderson et al ., ), and thus, may have caused spore‐forming or taxa with low fitness to persist in the P addition treatments. Under the N and MN treatments with intermediate disturbance intensity and stable effective amount of soil resources (but the effective resource components have changed, as mentioned earlier), microbial gene richness showed positive responses (especially under the MN treatment).…”