Results for “AIMS Microbiology” — Page 2

USGS2022

Natural inactivation of MS2, poliovirus type 1 and Cryptosporidium parvum in an anaerobic and reduced aquifer

Aims The study of microbial inactivation rates in aquifer systems has most often been determined in aerobic and oxidized systems. This study examined the inactivation (i.e. loss of infectivity) of MS2, poliovirus type 1 (PV1) and Cryptosporidium parvum in an anaerobic and reduced groundwater system that has been identified as storage zones for aquifer storage and recovery (ASR) facilities. Methods and Results Anaerobic and reduced (ORP < − 250 mV) groundwater from an artesian well was diverted to an above-ground, flow-through mesocosm that contained diffusion chambers filled with MS2, PV1 or Cryptosporidium parvum . The respective infectivity assays were performed on microorganisms recovered from the diffusion chambers during 30- to 58-day experiments. The net reduction in infectivity was 5.73 log 10 over 30 days for MS2, 5.00 log 10 over 58 days for PV1 and 4.07 log 10 over 37 days for C . parvum . The best fit inactivation model for PV1 was the log-linear model and the Weibull model for MS2 and C . parvum , with respective inactivation rates (95% confidence interval) of 0.19 (0.17–0.21) log 10 day −1 , 0.31 (0.19–0.89) log 10 day −1 and 0.20 (0.14–0.37) log 10 day −1 . Conclusions The groundwater geochemical conditions in this aquifer enhanced the inactivation of MS2, PV1, and C . parvum at rates approximately 2.0–5.3-fold, 1.2–17.0-fold, and 4.5–5.6-fold greater, respectively, than those from published studies that used diffusion chambers in aerobic-to-anoxic groundwater systems, with positive redox potentials. Significance and Impact of the Study Geochemical conditions like those in the aquifer zone in this study can naturally and significantly reduce concentrations of microbial indicators and pathogens of human health concern in injected surface water. Appropriate storage times for injected surface water could complement above-ground engineered processes for microorganism removal and inactivation (e.g. filtration, disinfection) by naturally increasing overall microorganism log-inactivation rates of ASR facilities.

Journal of Applied Microbiology↗

USGS2025

Bacterial community diversity and potential eco-physiological roles in toxigenic blooms composed of Microcystis, Aphanizomenon or Planktothrix

Cyanobacterial toxicity, cyanotoxins, and their impact on aquatic ecosystems and human health are well documented. In comparison, less is known about bloom-associated bacterial communities. Co-occurring bacteria can influence bloom development, physiology and collapse, and may also provide a niche for pathogenic bacteria. Existing research focuses on the cyanosphere of Microcystis -dominated blooms, despite the increasing prevalence of filamentous genera ( Aphanizomenon and Planktothrix ). This pilot study aimed to broaden our understanding of the bacterial consortia attached to morphologically distinct cyanobacteria (coccoid and filamentous) dominating phytoplankton communities and to explore their potential roles in amplifying the impacts of cyanobacterial blooms. We investigated four shallow freshwater bodies across three continents and two climate zones: an urban pond in the USA, a dammed reservoir and a natural lake in Poland, and an urban water body in Singapore. Amplicon sequencing (16S rRNA gene) was used to characterize bacterial communities, while shotgun metagenomics identified nitrogen- and phosphorus-cycling genes to infer potential eco-physiological functions. Cyanobacteria dominated bacterioplankton assemblages at all sites (>35.6%), with bloom composition influencing toxigenic profiles. A mixed bloom of Microcystis , Snowella , and Aphanizomenon had the broadest range of cyanotoxin synthetase genes ( mcy E, cyr J, ana F and sxt A). Microcystis blooms correlated with increased Roseomonas , while Planktothrix co-occurred with Flavobacterium – both bacteria likely contribute to nutrient-cycling within blooms and represent potential opportunistic pathogens for aquatic organisms and humans. The Microcystis cyanosphere exhibited the highest number of significant positive correlations with bacteria (19 relations), compared to Planktothrix and Aphanizomenon (11 and 2 relations, respectively). Non-diazotrophic blooms of Microcystis and Planktothrix showed greater abundances of nitrogen – ( ure B, gln A, nar B, and nar HZ) and phosphorus-cycling genes ( pho BHPR and ppk 1), indicating a strong dependence on associated bacteria for nutrient acquisition compared to diazotrophic Aphanizomenon . These findings suggest that Aphanizomenon -dominated blooms may be sustained by simpler microbiomes. Our results provide preliminary evidence of cyanosphere heterogeneity potentially shaped by the dominance or coexistence of three morphologically and eco-physiologically distinct genera of cyanobacteria. A comprehensive knowledge of the taxonomy and functional roles of bloom-associated microbiomes is therefore essential to understand bloom activity, evaluate the environmental threat, and develop effective strategies for prevention and mitigation.

Frontiers in Microbiology↗