Naegleria fowleri is a free-living protozoa that resides in soil and freshwater. Human intranasal amoebae exposure through water or potentially dust particles can culminate in primary amoebic meningoencephalitis (PAM), which generally causes death. While many questions remain regarding pathogenesis, the microbial ecology of N. fowleri is even less understood. This review outlines current knowledge of the environmental abiotic and biotic factors that affect the distribution and abundance of N. fowleri. Although the impacts of some abiotic factors remain poorly investigated or inconclusive, N. fowleri appears to have a wide pH range, low salinity tolerance, and thermophilic preference. From what is known about biotic factors, the amoebae preferentially feed upon bacteria and are preyed upon by other free-living amoebae. Additional laboratory and environmental studies are needed to fill in knowledge gaps, which are crucial for surveillance and management of N. fowleri in freshwaters. As surface water temperatures increase with climate change, it is likely that this amoeba will pose a greater threat to human health, suggesting that identifying its abiotic and biotic preferences is critical to mitigating this risk.

Anthropogenic habitat disturbances can dramatically alter ecological community interactions, including host-pathogen dynamics. Recent work has highlighted the potential for habitat disturbances to alter hostassociated microbial communities, but the associations between anthropogenic disturbance, host microbiomes, and pathogens are unresolved. Amphibian skin microbial communities are particularly responsive to factors like temperature, physiochemistry, pathogen infection, and environmental microbial reservoirs. Through a eld survey on wild populations of Acris crepitans (Hylidae) and Lithobates catesbeianus (Ranidae), we assessed effects of habitat disturbance on environmental bacterial resevoirs, Batrachochytrium dendrobatidis (Bd) infection, and skin microbiome composition. We found higher measures of microbiome dispersion (a measure of community stability) in A. crepitans from more disturbed ponds, supporting the hypothesis that disturbance increases stochasticity in biological communties. We also found that habitat disturbance limited microbiome similarity between locations for both species, suggesting less bacterial exchange in more disturbed areas. Higher disturbance was associated with lower Bd prevalence for A. crepitans, which could signify suboptimal microclimates for Bd in disturbed habitats. In this system we use microbiome dispersion as a metric of population health. Combined, our ndings show that reduced microbiome stability stemming from habitat disturbance could compromise population health, even in the absence of pathogenic infection.

Naegleria fowleri causes primary amoebic meningoencephalitis, a deadly infection that occurs when free‐living amoebae enter the nose via freshwater and travel to the brain. N. fowleri naturally thrives in freshwater and soil and is thought to be associated with elevated water temperatures. While environmental and laboratory studies have sought to identify what environmental factors influence its presence, many questions remain. This study investigated the interactive effects of temperature, pH, and salinity on N. fowleri in deionized and environmental waters. Three temperatures (15, 25, 35°C), pH values (6.5, 7.5, 8.5), and salinity concentrations (0.5%, 1.5%, 2.5% NaCl) were used to evaluate the growth of N. fowleri via ATP luminescent assays. Results indicated N. fowleri grew best at 25°C, and multiple interactive effects occurred between abiotic factors. Interactions varied slightly by water type but were largely driven by temperature and salinity. Lower temperature increased N. fowleri persistence at higher salinity levels, while low salinity (0.5% NaCl) supported N. fowleri growth at all temperatures. This research provided an experimental approach to assess interactive effects influencing the persistence of N. fowleri. As climate change impacts water temperatures and conditions, understanding the microbial ecology of N. fowleri will be needed minimize pathogen exposure.

No abstract

Anthropogenic habitat disturbances can dramatically alter ecological community interactions, including host-pathogen dynamics. Recent work has highlighted the potential for habitat disturbances to alter host-associated microbial communities, but the associations between anthropogenic disturbance, host microbiomes, and pathogens are unresolved. Amphibian skin microbial communities are particularly responsive to factors like temperature, physiochemistry, pathogen infection, and environmental microbial reservoirs. Through a field survey on wild populations of Acris crepitans (Hylidae) and Lithobates catesbeianus (Ranidae), we assessed effects of habitat disturbance on environmental bacterial resevoirs, Batrachochytrium dendrobatidis (Bd) infection, and skin microbiome composition. We found higher measures of microbiome dispersion (a measure of community stability) in A. crepitans from more disturbed ponds, supporting the hypothesis that disturbance increases stochasticity in biological communties. We also found that habitat disturbance limited microbiome similarity between locations for both species, suggesting less bacterial exchange in more disturbed areas. Higher disturbance was associated with lower Bd prevalence for A. crepitans, which could signify suboptimal microclimates for Bd in disturbed habitats. In this system we use microbiome dispersion as a metric of population health. Combined, our findings show that reduced microbiome stability stemming from habitat disturbance could compromise population health, even in the absence of pathogenic infection.