Effects of Manure-Application Practices on Curli Production by Escherichia coli Transported through Soil

Abstract

The release of Escherichia coli into the environment from untreated manure can pose a threat to human health. Environmental survival of E. coli has been linked to extracellular fibers called curli. We investigated the effect of manure management (surface application followed by incorporation versus immediate incorporation) on the relative abundance of curli-producing E. coli in subsurface drainage effluent. Samples were collected from three dairy farms. The proportion of curli-producing E. coli in the manure storage facilities was uniform across the farms. However, the abundance of curli-producing E. coli was much greater (P < 0.05) in the tile drains of farms performing surface application of manure than in the tile drain of the farm that incorporated manure. This field observation was tested with controlled soil column experiments; the abundance of curli-producing E. coli in soil column effluents was greater (P < 0.05) when manure was surface-applied than when it was incorporated. Our findings suggest selection pressures resulting from the different manure application methods affected curli production by E. coli isolates transported through soil. Given the importance of curli production in pathogenesis, this work highlights the effect that manure management strategies may have on pathogenesis-associated phenotypes of bacteria in agricultural subsurface runoff.

Absence of Curli in Soil-Persistent Escherichia coli Is Mediated by a C-di-GMP Signaling Defect and Suggests Evidence of Biofilm-Independent Niche Specialization

“…Bioinformatic analyses of some of the main genes required for curli production (such as csgD , csgB , csgA and csgD promoters) revealed wild type alleles in the strains lacking curli production. The presence of wild type curli subunit genes in E. coli strains do not always result in curli production and this has been reported by several authors in E. coli ( Dyer et al, 2007 ; Truhlar et al, 2015 ), Salmonella spp. ( De Oliveira et al, 2014 ) and Enterobacter sakazakii ( Zogaj et al, 2003 ).…”

“…The heterogeneity in curli production may reflect the genetic diversity of E. coli lineages present in the soil, perhaps suggesting that they have evolved to occupy different localized niches in the soil, with some of the niches not requiring the ability to retain curli. Evidence supporting this hypothesis comes from a study by Truhlar et al (2015) , which showed that the population of E. coli curli producers was maintained at a higher level when manure was spread on the surface of the soil than when it was injected into the soil. The selection for retention of curli on the soil surface was proposed to be based on a need for protective biofilm to help overcome UV radiation and desiccation, which would not be encountered below the soil surface ( Truhlar et al, 2015 ).…”

“…Production of curli correlated with a higher level of biofilm production ( Somorin et al, 2016 ) and attachment to a component of many soils (quartz sand) ( Figure 8 ). Curli production has been shown to contribute to survival in manure-amended soil ( Truhlar et al, 2015 ). Our data show that loss of biofilm/attachment does not affect long-term soil persistence, suggesting that some E. coli may occupy non-biofilm niches in the soil.…”

“…More recently, Yad fimbriae were demonstrated to promote E. coli adherence to plants, animal cells and promote persistence in the environment ( Larsonneur et al, 2016 ). Production of biofilm enhances the survival of Salmonella in a dry and nutrient-depleted environment ( Vestby et al, 2009 ) and of E. coli in soil ( Truhlar et al, 2015 ). Biofilm has also been shown to promote the persistence of E. coli on fresh produce ( Annous et al, 2009 ) and in food processing environments ( Silagyi et al, 2009 ; Maal-Bared et al, 2013 ).…”

Cover Crop and Fertility Effects on Escherichia coli Abundance in a Composted Poultry Litter-Amended Silt Loam Soil

“…Untreated manure can carry harmful bacteria (e.g., pathogens) to soil, which can survive for weeks and transfer to the edible crop parts with time [16]. Land-application of animal manure also enables bacterial pathogens to reach groundwater and adversely affect ecosystem and human health [17][18][19][20]. ough it is normally a benign commensal organism and used as a proxy for enteric pathogens, several E. coli strains are pathogenic and can cause severe hemorrhagic colitis and hemolytic uremia in humans [15,[21][22][23].…”