Biology subjects

Hudson, L. K.

Publications and source records attributed to Hudson, L. K..

3 recordsLinked to original sources

bioRxiv2022

Phenotypic characterization and analysis of complete genomes of two distinct strains of the proposed species "L. swaminathanii"

Recently, a new Listeria species, "Listeria swaminathanii", was proposed. Here, we phenotypically and genotypically characterize two additional strains that were previously obtained from soil samples and compare the results to the type strain. Complete genomes for both strains were assembled from hybrid Illumina and Nanopore sequencing reads and annotated. Further genomic analysis including average nucleotide identity (ANI) and detection of mobile genetic elements and genes of interest (e.g., virulence-associated) were conducted. The strains showed 98.7-98.8% ANI with the type strain. The UTK C1-0015 genome contained a partial monocin locus and a plasmid while the UTK C1-0024 genome contained a full monocin locus and a prophage. Phenotypic characterization consistent with those performed on the proposed type strain was conducted to assess consistency of phenotypes across a greater diversity of the proposed species (n=3 instead of n=1). Only a few findings were notably different from those of the type strain, such as catalase activity, glycerol metabolism, starch metabolism, and growth at 41{degrees}C. This study further expands our understanding of this newly proposed sensu stricto Listeria species.

microbiology↗

bioRxiv2021

Soil collected in the Great Smoky Mountains National Park yielded a novel Listeria species, L. swaminathanii, effectively expanding the sensu stricto clade to ten species

Soil samples collected in the Great Smoky Mountains National Park yielded a Listeria isolate that could not be classified to the species level. Whole-genome sequence-based average nucleotide identity BLAST and in silico DNA-DNA Hybridization analyses confirmed this isolate to be a novel Listeria sensu stricto species with the highest similarity to L. marthii (ANI=93.9%, isDDH=55.9%). Additional whole-genome-based analysis using the Genome Taxonomy Database Toolkit, an automated program for classifying bacterial genomes, further supported delineation as a novel Listeria sensu stricto species, as this tool failed to assign a species identification but identified L. marthii as the closest match. Phenotypic and genotypic characterization results indicate that this species is nonpathogenic. Specifically, the novel Listeria species described here is phenotypically (i) non-hemolytic and (ii) negative for phosphatidylinositol-specific phospholipase C activity; the draft genome lacks all virulence genes found in the Listeria pathogenicity island 1 (LIPI-1), as well as the internalin genes inlA and inlB. While the type strain for the new species is phenotypically catalase-negative (an unusual characteristic for Listeria sensu stricto species), its genome contained an apparently intact catalase gene (kat); hence assessment of this phenotype with future isolates will be important. Rapid species identification systems (Listeria API, VITEK 2, VITEK MS) misidentified this novel species as either L. monocytogenes, L. innocua, or L. marthii. We propose the name L. swaminathanii, and the type strain is FSL L7-0020T (=ATCC TSD-239T). IMPORTANCEL. swaminathanii is a novel sensu stricto species that originated from a US National Park, and its place of origin is ultimately preventing this species from achieving valid status. The US National Park Service restricts strain accessibility and open access is currently a prerequisite for species validation. Essentially the only criteria that was not met for L. swaminathanii validation is accessibility of the type strain, therefore nomenclature status should not negate the significance of this discovery. As a novel sensu stricto species, L. swaminathanii expands the group of species whose presence is associated with an increased risk of an L. monocytogenes contamination, and therefore could play an important role in public health. While developers of Listeria spp. detection methods historically only included validly publish species in their validation studies, L. swaminathanii is unequivocally a sensu stricto species and should be included as well.

microbiology↗

bioRxiv2021

Listeria spp. Isolated from Soil Samples Collected in the Great Smoky Mountains

Listeria monocytogenes, a foodborne pathogen, and other Listeria spp. are present in natural environments. Isolating and characterizing strains from natural reservoirs can provide insight into the prevalence and diversity of Listeria spp. in these environments, elucidate their contribution to contamination of agricultural and food processing environments and food products, and lead to the discovery of novel species. In this study, we evaluated the diversity of Listeria spp. isolated from soil samples in a small region of the Great Smoky Mountains National Park (GSMNP), which is the most biodiverse national park in the United States National Park system. Of the 17 Listeria isolates that were recovered, whole-genome sequencing revealed that 14 were unique strains. The unique strains were shown to represent a diversity of Listeria spp., including L. monocytogenes (n=9), L. cossartiae subsp. cossartiae (n=1), L. marthii (n=1), L. booriae (n=1), and a novel Listeria sp. (n=2). The Listeria isolated in this study were collected from high elevation sites near a creek that drains into a series of rivers ultimately leading to the Mississippi River; thus, the Listeria present in this natural environment could potentially travel downstream to a large region that includes portions of nine southeastern and midwestern states in the U.S. The Listeria spp. isolated and described in this study provide insight into the diversity of Listeria spp. found in the Great Smoky Mountains and indicate that this environment is a reservoir of novel Listeria spp. IMPORTANCEListeria monocytogenes is a foodborne pathogen that can cause serious systemic illness that, although rare, usually results in hospitalization and has a relatively high mortality rate compared to other foodborne pathogens. Identification of novel and diverse Listeria spp. provides insight into the genomic evolution, ecology, and evolution and variance of pathogenicity of this genus, especially in natural environments. Comparing L. monocytogenes and Listeria spp. isolates from natural environments, such as those recovered in this study, to contamination and/or outbreak strains may provide more information about the original natural sources of these strains and the pathways and mechanisms that lead to contamination of food products and agricultural or food processing environments.

microbiology↗