Biotic and Abiotic Soil Properties Influence Survival of Listeria monocytogenes in Soil

Self Cite

In this study, we investigated whether the Agr-mediated response is triggered during adaptation in soil, and we compared survival patterns in a set of 10 soils. The fate of the parental strain L. monocytogenes L9 (a rifampin-resistant mutant of L. monocytogenes EGD-e) and that of a ⌬agrA deletion mutant were compared in a collection of 10 soil microcosms. The ⌬agrA mutant displayed significantly reduced survival in these biotic soil microcosms, and differential transcriptome analyses showed large alterations of the transcriptome when AgrA was not functional, while the variations in the transcriptomes between the wild type and the ⌬agrA deletion mutant were modest under abiotic conditions. Indeed, in biotic soil environments, 578 protein-coding genes and an extensive repertoire of noncoding RNAs (ncRNAs) were differentially transcribed. The transcription of genes coding for proteins involved in cell envelope and cellular processes, including the phosphotransferase system and ABC transporters, and proteins involved in resistance to antimicrobial peptides was affected. Under sterilized soil conditions, the differences were limited to 86 genes and 29 ncRNAs. These results suggest that the response regulator AgrA of the Agr communication system plays important roles during the saprophytic life of L. monocytogenes in soil. Listeria monocytogenes is the causative agent of listeriosis, a serious foodborne infection affecting essentially immunocompromised individuals, the elderly, and pregnant women (1). The pathogen is largely spread in the environment. It has been isolated from water systems (2-4), vegetation (5), soil (6-8), farms (9-12), food industries (13-15), and the feces of animals (16-18). Environmental adaptation requires that the cell have the ability to integrate environmental cues in order to adapt its physiology to the surrounding conditions through the regulation of gene expression. Genomics showed that an important part of the L. monocytogenes genome (7.3%) is dedicated to regulation and includes 209 transcriptional regulators, 15 histidine kinases, and 16 response regulators constituting two-component systems (19). Two-component systems participate in the ability of bacteria to sense and respond to fluctuating environmental conditions. AgrC/AgrA is a two-component regulatory system that is part of the Agr communication system. Initially described in Staphylococcus aureus, this communication system is organized as a four-gene operon, agrBDCA. AgrB is a membrane-bound protein that processes the propeptide AgrD into a mature autoinducing peptide (AIP). Detection of AIP by the histidine kinase AgrC induces transcriptional regulation through activation of the regulator AgrA. Detailed data concerning the role of the Agr system in the physiology of S. aureus are available (20)(21)(22). So far, its role in the adaptation of L. monocytogenes to its environment is only partially understood (23). Reports show that the Agr communication system of L. monocytogenes is involved in adhesion to abiotic surfaces (24) in ...

Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Survival of Listeria monocytogenes in Soil Requires AgrA-Mediated Regulation

Vivant

Garmyn

Gal

et al. 2015

Self Cite

“…Important factors that have been speculated to influence the occurrence of L. monocytogenes in soil are soil microbiota, fauna, soil composition, temperature, pH, moisture, and strain motility (2,26,27,28). However, if further insight is to be gained into the unique ecological behavior of L. monocytogenes, it is necessary to map globally occurring genotypes and strains from environmental habitats (29,30).…”

Section: T He Genus Listeria Comprises the Species L Monocytogenes mentioning

confidence: 99%

Reservoirs of Listeria Species in Three Environmental Ecosystems

Linke

Rückerl

Brugger

et al. 2014

165

182

Soil and water are suggested to represent pivotal niches for the transmission of Listeria monocytogenes to plant material, animals, and the food chain. In the present study, 467 soil and 68 water samples were collected in 12 distinct geological and ecological sites in Austria from 2007 to 2009. Listeria was present in 30% and 26% of the investigated soil and water samples, respectively. Generally, the most dominant species in soil and water samples were Listeria seeligeri, L. innocua, and L. ivanovii. The human-and animal-pathogenic L. monocytogenes was isolated exclusively from 6% soil samples in regions A (mountainous region) and B (meadow). Distinct ecological preferences were observed for L. seeligeri and L. ivanovii, which were more often isolated from wildlife reserve region C (Lake Neusiedl) and from sites in proximity to wild and domestic ruminants (region A). The higher L. monocytogenes detection and antibiotic resistance rates in regions A and B could be explained by the proximity to agricultural land and urban environment. L. monocytogenes multilocus sequence typing corroborated this evidence since sequence type 37 (ST37), ST91, ST101, and ST517 were repeatedly isolated from regions A and B over several months. A higher L. monocytogenes detection and strain variability was observed during flooding of the river Schwarza (region A) and Danube (region B) in September 2007, indicating dispersion via watercourses.

“…Soil type greatly determines the soil water content. The extended survival of nonpathogenic E. coli and E. coli O157:H7 has been attributed to higher water availability in different soil types (39) and to moisture content (40), while the long-term survival of Listeria monocytogenes in soil has been attributed to soil texture and clay content (41,42). Sandy soils, like the soil in our study, retain less water and have been associated with faster declines in E. coli (43).…”

Section: Discussionmentioning

confidence: 50%

Effects of Cover Crop Species and Season on Population Dynamics of Escherichia coli and Listeria innocua in Soil

Reed-Jones

Marine

Everts

et al. 2016

dCover crops provide several ecosystem services, but their impact on enteric bacterial survival remains unexplored. The influence of cover cropping on foodborne pathogen indicator bacteria was assessed in five cover crop/green manure systems: cereal rye, hairy vetch, crimson clover, hairy vetch-rye and crimson clover-rye mixtures, and bare ground. Cover crop plots were inoculated with Escherichia coli and Listeria innocua in the fall of 2013 and 2014 and tilled into the soil in the spring to form green manure. Soil samples were collected and the bacteria enumerated. Time was a factor for all bacterial populations studied in all fields (P < 0.001). E. coli levels declined when soil temperatures dipped to <5°C and were detected only sporadically the following spring. L. innocua diminished somewhat but persisted, independently of season. In an organic field, the cover crop was a factor for E. coli in year 1 (P ‫؍‬ 0.004) and for L. innocua in year 2 (P ‫؍‬ 0.011). In year 1, E. coli levels were highest in the rye and hairy vetch-rye plots. In year 2, L. innocua levels were higher in hairy vetch-rye (P ‫؍‬ 0.01) and hairy vetch (P ‫؍‬ 0.03) plots than in the rye plot. Bacterial populations grew (P < 0.05) or remained the same 4 weeks after green manure incorporation, although initial reductions in L. innocua numbers were observed after tilling (P < 0.05). Green manure type was a factor only for L. innocua abundance in a transitional field (P < 0.05). Overall, the impacts of cover crops/green manures on bacterial population dynamics in soil varied, being influenced by bacterial species, time from inoculation, soil temperature, rainfall, and tillage; this reveals the need for long-term studies. In agricultural environments, soil can serve as a reservoir and route of transmission for foodborne pathogens (1). Since fresh produce is often consumed raw without a "kill step" to inactivate human-pathogenic microorganisms, it is important to prevent the contamination of these foods during production (2). Growers may implement good agricultural practices (GAPs) to minimize the risk of produce contamination at the preharvest level (3), as this program focuses on on-farm risk factors, including animalbased fertilizers, irrigation water quality, farm worker training and hygiene, and wildlife exclusion. Outbreaks and contamination events, however, continue to occur, emphasizing the need to evaluate the role of other agricultural practices, which thus far have received less attention, on enteric pathogen dynamics on a farm.One such practice is cover cropping, the establishment of a crop, typically a small grain or legume, in between cultivations of a cash crop. In recent years, economic and environmental considerations have renewed interest in this old practice for improving crop productivity and soil health and maintaining the sustainability of agroecosystems (4). Cover cropping brings a variety of ecosystem services to agricultural systems, including seasonal protection of soil from erosion, weed suppression, soil improvement, a...