Search

Microbial communities are essential for a healthy soil ecosystem. Metals and radionuclides can exert a persistent pressure on the soil microbial community. However, little is known on the effect of long-term co-contamination of metals and radionuclides on the microbial community structure and functionality. We investigated the impact of historical discharges of the phosphate and nuclear industry on the microbial community in the Grote Nete river basin in Belgium. Eight locations were sampled along a transect to the river edge and one location further in the field. Chemical analysis demonstrated a metal and radionuclide contamination gradient and revealed a distinct clustering of the locations based on all metadata. Moreover, a relation between the chemical parameters and the bacterial community structure was demonstrated. Although no difference in biomass was observed between locations, cultivation-dependent experiments showed that communities from contaminated locations survived better on singular metals than communities from control locations. Furthermore, nitrification, a key soil ecosystem process seemed affected in contaminated locations when combining metadata with microbial profiling. These results indicate that long-term metal and radionuclide pollution impacts the microbial community structure and functionality and provides important fundamental insights into microbial community dynamics in co-metal-radionuclide contaminated sites., (© 2021 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.)

Interactions between microorganisms and rocks play an important role in Earth system processes. However, little is known about the molecular capabilities microorganisms require to live in rocky environments. Using a quantitative label-free proteomics approach, we show that a model bacterium (Cupriavidus metallidurans CH34) can use volcanic rock to satisfy some elemental requirements, resulting in increased rates of cell division in both magnesium- and iron-limited media. However, the rocks also introduced multiple new stresses via chemical changes associated with pH, elemental leaching and surface adsorption of nutrients that were reflected in the proteome. For example, the loss of bioavailable phosphorus was observed and resulted in the upregulation of diverse phosphate limitation proteins, which facilitate increase phosphate uptake and scavenging within the cell. Our results revealed that despite the provision of essential elements, rock chemistry drives complex metabolic reorganization within rock-dwelling organisms, requiring tight regulation of cellular processes at the protein level. This study advances our ability to identify key microbial responses that enable life to persist in rock environments., (© 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.)

As a ubiquitous environmental organism that is occasionally part of the human flora, Pseudomonas aeruginosa could pose a health hazard for the immunocompromised astronauts during long-term missions. Therefore, insights into the behaviour of P. aeruginosa under spaceflight conditions were gained using two spaceflight-analogue culture systems: the rotating wall vessel (RWV) and the random position machine (RPM). Microarray analysis of P. aeruginosa PAO1 grown in the low shear modelled microgravity (LSMMG) environment of the RWV, compared with the normal gravity control (NG), revealed an apparent regulatory role for the alternative sigma factor AlgU (RpoE-like). Accordingly, P. aeruginosa cultured in LSMMG exhibited increased alginate production and upregulation of AlgU-controlled transcripts, including those encoding stress-related proteins. The LSMMG increased heat and oxidative stress resistance and caused a decrease in the oxygen transfer rate of the culture. This study also showed the involvement of the RNA-binding protein Hfq in the LSMMG response, consistent with its previously identified role in the Salmonella LSMMG and spaceflight response. The global transcriptional response of P. aeruginosa grown in the RPM was highly similar to that in NG. Fluid mixing was assessed in both systems and is believed to be a pivotal factor contributing to transcriptional differences between RWV- and RPM-grown P. aeruginosa. This study represents the first step towards the identification of virulence mechanisms of P. aeruginosa activated in response to spaceflight-analogue conditions, and could direct future research regarding the risk assessment and prevention of Pseudomonas infections during spaceflight and in immunocompromised patients.