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Sleight, Sean C.; Wigginton, Nicholas S.; Lenski, Richard E.

doi:10.1186/1471-2148-6-104

Cited by 39 publications

(19 citation statements)

References 37 publications

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“…This may be due to the fact that the water mesocosms remained frozen and did not thaw under the F–T cycle, whereas the faecal matrix, assumed to offer protection, likely experienced recrystalisation during the F–T cycling, resulting in a more detrimental effect on E. coli physiology. This would be consistent with suggestions that cell viability under freezing conditions is influenced more by repeated freeze–thawing than the duration of exposure to freezing conditions [ 33 ]. Survival curves of intestinal enterococci sourced from dairy cows and exposed to the lower F–T regime accommodated higher λ values in water relative to faeces but, as with E. coli , their final concentration in water was maintained at a higher level than the population held within the faeces.…”

Section: Discussionsupporting

confidence: 92%

Impact of Freeze–Thaw Cycles on Die-Off of E. coli and Intestinal Enterococci in Deer and Dairy Faeces: Implications for Landscape Contamination of Watercourses

Afolabi¹,

Oliver²

2020

IJERPH

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Characterising faecal indicator organism (FIO) survival in the environment is important for informing land management and minimising public health risk to downstream water users. However, key gaps in knowledge include understanding how wildlife contribute to catchment-wide FIO sources and how FIO survival is affected by low environmental temperatures. The aim of this study was to quantify E. coli and intestinal enterococci die-off in dairy cow versus red deer faecal sources exposed to repeated freeze–thaw cycles under controlled laboratory conditions. Survival of FIOs in water exposed to freeze–thaw was also investigated to help interpret survival responses. Both E. coli and intestinal enterococci were capable of surviving sub-freezing conditions with the faeces from both animals able to sustain relatively high FIO concentrations, as indicated by modelling, and observations revealing persistence in excess of 11 days and in some cases confirmed beyond 22 days. Die-off responses of deer-derived FIOs in both faeces and water exposed to low temperatures provide much needed information to enable better accounting of the varied catchment sources of faecal pollution and results from this study help constrain the parameterisation of die-off coefficients to better inform more integrated modelling and decision-making for microbial water quality management.

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Section: Discussionsupporting

confidence: 92%

Impact of Freeze–Thaw Cycles on Die-Off of E. coli and Intestinal Enterococci in Deer and Dairy Faeces: Implications for Landscape Contamination of Watercourses

Afolabi¹,

Oliver²

2020

IJERPH

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“…BGI-2 was subjected to freeze thaw cycles to check its survivability/tolerance against freezing and freeze thaw cycles without the addition of any external cryoprotective agent. This test was performed by colony count method as described previously with some modifications (Sleight et al, 2006;Shivaji et al, 2013). Survivability of BGI-2 was compared with another psychrotrophic non-EPS producing Rhodococcus sp.…”

Section: Nmr Spectroscopy Of the Eps Preparationsmentioning

confidence: 99%

A Glacier Bacterium Produces High Yield of Cryoprotective Exopolysaccharide

et al. 2020

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Pseudomonas sp. BGI-2 is a psychrotrophic bacterium isolated from the ice sample collected from Batura glacier, Pakistan. This strain produces highly viscous colonies on agar media supplemented with glucose. In this study, we have optimized growth and production of exopolysaccharide (EPS) by the cold-adapted Pseudomonas sp. BGI-2 using different nutritional and environmental conditions. Pseudomonas sp. BGI-2 is able to grow in a wide range of temperatures (4-35 • C), pH (5-11), and salt concentrations (1-5%). Carbon utilization for growth and EPS production was extensively studied and we found that glucose, galactose, mannose, mannitol, and glycerol are the preferable carbon sources. The strain is also able to use sugar waste molasses as a growth substrate, an alternative for the relatively expensive sugars for large scale EPS production. Maximum EPS production was observed at 15 • C, pH 6, NaCl (10 g L −1), glucose as carbon source (100 g L −1), yeast extract as nitrogen source (10 g L −1), and glucose/yeast extract ratio (10/1). Under optimized conditions, EPS production was 2.01 g L −1 , which is relatively high for a Pseudomonas species compared to previous studies using the same method for quantification. High-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) analysis of EPS revealed glucose, galactose, and glucosamine as the main sugar monomers. Membrane protection assay using human RBCs revealed significant reduction in cell lysis (∼50%) in the presence of EPS, suggesting its role in membrane protection. The EPS (5%) also conferred significant cryoprotection for a mesophilic Escherichia coli k12 which was comparable to glycerol (20%). Also, improvement in lipid peroxidation inhibition (in vitro) resulted when lipids from the E. coli was pretreated with EPS. Increased EPS production at low temperatures, freeze thaw tolerance of the EPS producing strain, and increased survivability of E. coli in the presence of EPS as cryoprotective agent supports the hypothesis that EPS production is a strategy for survival in extremely cold environments such as the glacier ice.

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“…However, in many other cases parallel phenotypic changes occur not because they are advantageous, but because of relaxed selection and mutation accumulation. For example, numerous studies have shown that adaptation in the LTEE leads to a reduction in catabolic breadth and thermal-tolerance in E. coli (Bennett and Lenski 2007; Cooper et al 2001a; Cooper and Lenski 2000; Cooper et al 2001b; Leiby and Marx 2014; Sleight et al 2006). …”

Section: Realizing the Promise Of Experimental Evolutionmentioning

confidence: 99%

The spectrum of adaptive mutations in experimental evolution

Lang

Desai

2014

Genomics

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A primary goal of recent work in experimental evolution is to probe the molecular basis of adaptation. This requires an understanding of the individual mutations in evolving populations: their identity, their physiological and fitness effects, and the interactions between them. The combination of high-throughput methods for laboratory evolution and next-generation sequencing methods now make it possible to identify and quantify mutations in hundreds of replicate populations over thousands of generations, and to directly measure fitness effects and epistatic interactions. Many laboratories are now leveraging these tools to study the molecular basis of adaptation and the reproducibility of evolutionary outcomes across a variety of model systems. Genetic analyses on evolved populations are shedding light on the statistics of epistasis between evolved mutations. Here we review the current understanding of the spectrum of mutations observed across these systems, with a focus on epistatic interactions between beneficial mutations and constraints on evolutionary outcomes. We emphasize evolution in asexual microbes, where next generation sequencing methods have been widely applied.

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Untitled

Cited by 39 publications

References 37 publications

Impact of Freeze–Thaw Cycles on Die-Off of E. coli and Intestinal Enterococci in Deer and Dairy Faeces: Implications for Landscape Contamination of Watercourses

Impact of Freeze–Thaw Cycles on Die-Off of E. coli and Intestinal Enterococci in Deer and Dairy Faeces: Implications for Landscape Contamination of Watercourses

A Glacier Bacterium Produces High Yield of Cryoprotective Exopolysaccharide

The spectrum of adaptive mutations in experimental evolution

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