Microbial Interactions — Underexplored Links Between Public Health Relevant Bacteria and Protozoa in Coastal Environments

Abstract

The co-existence of bacteria and protozoa in aquatic environments has led to the evolution of predation defense mechanisms by the bacteria. Some of the predation-resistant bacteria (PRB) are also pathogenic to humans and other mammals. The links between PRB and protozoa in natural aquatic systems are poorly known, but they are important in predicting outbreaks and determining the long-term consequences of a contamination event. To elucidate co-occurrence patterns between PRB (16S rRNA) and bacterivorous protozoa (18S rRNA), we performed a field study in a coastal area in the northern Baltic Sea. Interactions between bacteria and protozoa were explored by using two complementary statistical tools. We found co-occurrence patterns between specific PRB and protozoa, such as Legionella and Ciliophora, and we also found that the interactions are genotype-specific as, for example, Rickettsia. The PRB sequence diversity was larger in bays and freshwater inlets compared to offshore sites, indicating local adaptions. Considering the PRB diversity in the freshwater in combination with the large spring floods in the area, freshwater influxes should be considered a potential source of PRB in the coastal northern Baltic Sea. These findings are relevant for the knowledge of survival and dispersal of potential pathogens in the environment.

Co-occurrences enhance our understanding of aquatic fungal metacommunity assembly and reveal potential host–parasite interactions

“…Samplings were conducted by following the course of four freshwater inlets towards the brackish water of the Gulf of Bothnia, northern Baltic Sea. Four surface water samples were collected (0.5 m depth) once in a month in these four bays during the summer period (June to September) in 2018 (Eriksson et al 2022 ). In addition, samples from two offshore sites were also collected in each month (Fig.…”

Co-occurrences enhance our understanding of aquatic fungal metacommunity assembly and reveal potential host–parasite interactions

“…All water samples were collected in sterile sampling bottles, then transported to the laboratory and stored in the dark at 4 °C. Physicochemical properties of samples were measured (Eriksson et al 2022) and included in this study.…”

“…With the aim to further investigate biotic interactions and, in particular, potential parasitic-host associations, co-occurrence network was constructed. In parallel to this study, 18S V6-V8 rRNA gene sequences have been generated using the same samples (Eriksson et al 2022) and the subset of that dataset was used to assess potential host–parasitic(saprotrophic) associations in our bay samples (n = 40). Absolute read counts were used for the network analysis because previous studies have shown that relative abundance data suffer from apparent correlations which lower specificity of association networks (Berry & Widder 2014, Meng et al 2021).…”

“…Samplings were conducted by following the course of four freshwater inlets towards the brackish water of the Gulf of Bothnia, northern Baltic Sea. Four surface water samples were collected (0.5 m depth) once in a month in these four bays during the summer period (June to September) in 2018 (Eriksson et al 2022). In addition, samples from two offshore sites were also collected in each month (Fig.…”

“…All water samples were collected in sterile sampling bottles, then transported to the laboratory and stored in the dark at 4 °C. Physicochemical properties of samples were measured (Eriksson et al 2022) and included in this study. Briefly, temperature, pH and salinity were measured in situ with a WTW ProfiLine Cond 3110 portable device, and subsamples were used to measure environmental variables including dissolved organic carbon (DOC), total dissolved nutrients (TDP, TDN), dissolved inorganic nutrients (e.g., PO 4 3-, NH 4 + , NO 2 -, NO 3 -, SiO 2 ), and humic substances.…”