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Fecal indicator bacteria (FIB: Escherichia coli and enterococci) are used to assess recreational water quality. Viral indicators (i.e., somatic and F+ coliphage), could improve the prediction of viral pathogens in recreational waters, however, the impact of environmental factors, including the effect of predatory protozoa source, on their survival in water is poorly understood. We investigated the effect of lakewater or wastewater protozoa, on the decay (decreasing concentrations over time) of culturable FIB and coliphages under sunlight and shaded conditions. FIB decay was generally greater than the coliphages and was more rapid when indicators were exposed to lake vs. wastewater protozoa. F+ coliphage decay was the least affected by experimental variables. Somatic coliphage decayed fastest in the presence of wastewater protozoa and sunlight, though their decay under shaded conditions was-10-fold less than F+ after 14 days. The protozoa source consistently contributed significantly to the decay of FIB, and somatic, though not the F+ coliphage. Sunlight generally accelerated decay, and shade reduced somatic coliphage decay to the lowest level among all the indicators. Differential responses of FIB, somatic, and F+ coliphages to environmental factors support the need for studies that address the relationship between the decay of coliphages and viral pathogens under environmentally relevant conditions.

Supernatant proteins in Vibrio alginolyticus batch cultures were analyzed by SDS-PAGE before copper was added, 24 and 48 hours after the addition of copper, and in 24 hour control (no Cu) cultures. Two proteins, one 21 kilodalton (kDa) and one 19 kDa, were found to be copper-induced, and were designated copper-binding protein 1 (CuBP1) and CuBP2. CuBP1 and CuBP2 became detectable in supernatants during the Cu-induced lag phase, and increased in concentration over the following 48 hours. Chloramphenicol inhibited production of these proteins. Gel-to-gel variability was implicated as the dominant factor determining whether one or two Cu-induced proteins were detected in Vibrio alginolyticus supernatants, and ca. 20 kDa Cu-induced proteins were quantitated together in subsequent analyses. Experiments in continuous (chemostat) cultures of Vibrio alginolyticus demonstrated that the bacteria could survive copper stress in an open system. Copper stress reversibly inhibited swarming in most colonies from long-term copper-stressed cultures, and permanent inhibition of swarming was observed in some isolates. Mutation to an oxidase negative phenotype, which was not reversible, occurred at high frequency in copper-stressed continuous cultures. The stability of two Cur mutants isolated from continuous culture was demonstrated by subculturing each isolate ten times on nonselective marine agar (10° MA), and comparing plate counts on unamended and 40μM Cu-amended agar to corresponding plate counts of isolates freshly passed on Cu-amended agar. One Cur isolate, Cu40B3, constitutively produced a ca. 21 kDa protein which displayed the same chromatographic behavior (immobilized metal ion affinity chromatography followed by reverse phase high performance liquid chromatography) as CuBP. After fifteen nonselective subcultures, a revertant Cus derivative of Cu40B3 (Cu40B3(SW)) was isolated. Cu40B3(SW) lost the mutation to constitutive CuBP production and copper resistance simultaneously, indicating that constitutive CuBP production in Cu40B3 is necessary for maintenance of its copper-resistant phenotype. Copper-sensitive Vibrio alginolyticus mutants displayed a range of alterations in supernatant protein profiles, and two of the seven mutants were indistinguishable from the wild-type in terms of supernatant proteins with and without copper stress. One Cus mutant was isolated which contained no CuaP in supernatants from 50 μM copper-stressed cultures.

Vancomycin resistant enterococci (VRE) cause 20,000 infections annually in the United States, most of which are nosocomial. Recent findings of VRE in sewage-contaminated surface waters demonstrate an alternate route of human exposure, and a possible setting for horizontal gene exchange facilitated by plasmids and other mobile genetic elements. Maintenance of antibiotic resistance genes and proteins may, however, present a fitness cost in the absence of selective pressure, particularly in habitats such as environmental waters that are not optimal for gut-associated bacteria. Nutrient levels, which are transiently elevated following sewage spills, may also affect survival. We tested the hypotheses that nutrients and/or plasmids conferring vancomycin resistance affect Enterococcus faecium survival in river water by measuring decay of strains that differed only by their plasmid, under natural and augmented nutrient conditions. In natural river water, decay rate (logio reduction) correlated directly with plasmid size; however, plasmid presence and size had no effect on decay rate when nutrients levels were augmented. Under natural nutrient levels, the vancomycin-resistant strain with the largest plasmid (200 kb) decayed significantly more rapidly than the plasmid-less, susceptible parent strain, in contrast to similar decay rates among strains under augmented nutrient conditions. This work is among the first to show that plasmids conferring antibiotic resistance affect fitness of Enterococcus species in secondary habitats such as surface water. The nutrient-dependent nature of the fitness cost suggests that conveyance of VRE to environmental waters in nutrient-rich sewage may prolong survival of these pathogens, providing greater opportunity for host infection and/or horizontal gene transfer. (C) 2019 Published by Elsevier Ltd.

15 páginas.- 4 figuras.- 3 tablas.- 55 referencias.- SSupplemental material is available online only, The soil microbiome is a driver of nitrous oxide (N2O) emissions in terrestrial ecosystems. Identifying the core microbiome of N2O emissions and its temperature sensitivity from trillions of soil microorganisms is a great challenge and is essential to improving the predictability of soil-climate feedback related to increasing temperature. Here, the integrated soil microbiome covering archaeal, bacterial, fungal, algal, and microfaunal communities was studied to disengage the potential linkage with its N2O emissions and its temperature sensitivity in paddy fields by hunting for core species pairs. The results showed that between-group interactions of core bacterial and archaeal members and the within-group interactions of core bacterial members jointly contributed to the N2O emissions and its temperature sensitivity. The contribution of between-group interactions (32 to 33%) was greater than that of within groups (10 to 18%). These results suggested that N2O emissions and their fluctuations related to climate warming are affected by the within- and between-group interactions of the soil microbiome. Our results help advance the knowledge on the importance of microbial keystone species and network associations in controlling N2O production and their responses to increasing temperature. IMPORTANCE Soil microorganisms drive emissions of nitrous oxide from soils; this is a powerful greenhouse gas and the dominant ozone-depleting agent. N2O emissions can be partly predicted from soil properties and specific microbial groups, whereas a possible role of below-ground microbial interactions has largely been overlooked. Here, the integrated soil microbiome covering archaeal, bacterial, fungal, algal, and microfaunal communities was studied to disengage the potential linkage with the N2O emissions and temperature sensitivity of the microbiome in paddy fields by hunting for core species pairs. The results showed that between-group interactions of core bacterial and archaeal members and the within-group interactions of core bacterial members jointly contributed to the N2O emissions. The contribution of between-group interactions (32 to 33%) was greater than that of within-group interactions (10 to 18%). Our results help advance the knowledge on the importance of microbial keystone species and interactions in controlling N2O production and their responses to increasing temperature, This study was supported by the National Key R&D Program of China (2021YFD1900400), National Natural Science Foundation of China (41877060 and 42007027), Innovation Program of the Institute of Soil Science (ISSASIP2201), and the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2016284).