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September 22, 2019  |  

The Butanol Producing Microbe Clostridium beijerinckii NCIMB 14988 Manipulated Using Forward and Reverse Genetic Tools.

The solventogenic anaerobe Clostridium beijerinckii has potential for use in the sustainable bioconversion of plant-derived carbohydrates into solvents, such as butanol or acetone. However, relatively few strains have been extensively characterised either at the genomic level or through exemplification of a complete genetic toolkit. To remedy this situation, a new strain of C. beijerinckii, NCIMB 14988, is selected from among a total of 55 new clostridial isolates capable of growth on hexose and pentose sugars. Chosen on the basis of its favorable properties, the complete genome sequence of NCIMB 14988 is determined and a high-efficiency plasmid transformation protocol devised. The developed DNA transfer procedure allowed demonstration in NCIMB 14988 of the forward and reverse genetic techniques of transposon mutagenesis and gene knockout, respectively. The latter is accomplished through the successful deployment of both group II intron retargeting (ClosTron) and allelic exchange. In addition to gene inactivation, the developed allelic exchange procedure is used to create point mutations in the chromosome, allowing for the effect of amino acid changes in enzymes involved in primary metabolism to be characterized. ClosTron mediated disruption of the currently unannotated non-coding region between genes LF65_05915 and LF65_05920 is found to result in a non-sporulating phenotype.© 2018 The Authors. Biotechnology Journal Published by Wiley-VCH Verlag GmbH & Co. KGaA.

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September 22, 2019  |  

FRI-4 carbapenemase-producing Enterobacter cloacae complex isolated in Tokyo, Japan.

A carbapenem-resistant Enterobacter cloacae complex isolated in Tokyo, Japan, produced a carbapenemase that was detected by a Carba NP test and a modified carbapenem inactivation method, but none of the ‘Big Five’ carbapenemase genes was detected by PCR. This study aimed to identify the carbapenemase.Carbapenemase genes were screened by WGS. Next, we generated a recombinant plasmid in which the carbapenemase gene was inserted. We also extracted the carbapenemase gene-carrying plasmid from the E. cloacae complex. The effects of both plasmids on the antibiotic susceptibility of Escherichia coli were then tested. The carbapenemase gene-carrying plasmid in the E. cloacae complex was completely sequenced.A novel carbapenemase gene, blaFRI-4, encoded an amino acid sequence that was 93.2% identical to French imipenemase (FRI-1). E. coli transformed with blaFRI-4 showed reduced carbapenem susceptibility. A complete sequence of the blaFRI-4-carrying 98?508?bp IncFII/IncR plasmid (pTMTA61661) showed that blaFRI-4 and the surrounding region (18.7?kb) were duplicated.The FRI-4-producing E. cloacae complex was isolated in Japan, whereas all other FRI variants have been found in Europe, suggesting that the spread of FRI carbapenemases is global.

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September 22, 2019  |  

Genomic surveillance of Enterococcus faecium reveals limited sharing of strains and resistance genes between livestock and humans in the United Kingdom.

Vancomycin-resistant Enterococcus faecium (VREfm) is a major cause of nosocomial infection and is categorized as high priority by the World Health Organization global priority list of antibiotic-resistant bacteria. In the past, livestock have been proposed as a putative reservoir for drug-resistant E. faecium strains that infect humans, and isolates of the same lineage have been found in both reservoirs. We undertook cross-sectional surveys to isolate E. faecium (including VREfm) from livestock farms, retail meat, and wastewater treatment plants in the United Kingdom. More than 600 isolates from these sources were sequenced, and their relatedness and antibiotic resistance genes were compared with genomes of almost 800 E. faecium isolates from patients with bloodstream infection in the United Kingdom and Ireland. E. faecium was isolated from 28/29 farms; none of these isolates were VREfm, suggesting a decrease in VREfm prevalence since the last UK livestock survey in 2003. However, VREfm was isolated from 1% to 2% of retail meat products and was ubiquitous in wastewater treatment plants. Phylogenetic comparison demonstrated that the majority of human and livestock-related isolates were genetically distinct, although pig isolates from three farms were more genetically related to human isolates from 2001 to 2004 (minimum of 50?single-nucleotide polymorphisms [SNPs]). Analysis of accessory (variable) genes added further evidence for distinct niche adaptation. An analysis of acquired antibiotic resistance genes and their variants revealed limited sharing between humans and livestock. Our findings indicate that the majority of E. faecium strains infecting patients are largely distinct from those from livestock in this setting, with limited sharing of strains and resistance genes.IMPORTANCE The rise in rates of human infection caused by vancomycin-resistant Enterococcus faecium (VREfm) strains between 1988 to the 2000s in Europe was suggested to be associated with acquisition from livestock. As a result, the European Union banned the use of the glycopeptide drug avoparcin as a growth promoter in livestock feed. While some studies reported a decrease in VREfm in livestock, others reported no reduction. Here, we report the first livestock VREfm prevalence survey in the UK since 2003 and the first large-scale study using whole-genome sequencing to investigate the relationship between E. faecium strains in livestock and humans. We found a low prevalence of VREfm in retail meat and limited evidence for recent sharing of strains between livestock and humans with bloodstream infection. There was evidence for limited sharing of genes encoding antibiotic resistance between these reservoirs, a finding which requires further research. Copyright © 2018 Gouliouris et al.

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September 22, 2019  |  

A novel probiotic, Lactobacillus johnsonii 456, resists acid and can persist in the human gut beyond the initial ingestion period.

Probiotics are considered to have multiple beneficial effects on the human gastrointestinal tract, including immunomodulation, pathogen inhibition, and improved host nutrient metabolism. However, extensive characterization of these properties is needed to define suitable clinical applications for probiotic candidates. Lactobacillus johnsonii 456 (LBJ 456) was previously demonstrated to have anti-inflammatory and anti-genotoxic effects in a mouse model. Here, we characterize its resistance to gastric and bile acids as well as its ability to inhibit gut pathogens and adhere to host mucosa. While bile resistance and in vitro host attachment properties of LBJ 456 were comparable to other tested probiotics, LBJ 456 maintained higher viability at lower pH conditions compared to other tested strains. LBJ 456 also altered pathogen adhesion to LS 174T monolayers and demonstrated contact-dependent and independent inhibition of pathogen growth. Genome analyses further revealed possible genetic elements involved in host attachment and pathogen inhibition. Importantly, we show that ingestion of Lactobacillus johnsonii 456 over a one week yogurt course leads to persistent viable bacteria detectable even beyond the period of initial ingestion, unlike many other previously described probiotic species of lactic acid bacteria.

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September 22, 2019  |  

De novo assembly of the Pasteuria penetrans genome reveals high plasticity, host dependency, and BclA-like collagens.

Pasteuria penetrans is a gram-positive endospore forming bacterial parasite of Meloidogyne spp. the most economically damaging genus of plant parasitic nematodes globally. The obligate antagonistic nature of P. penetrans makes it an attractive candidate biological control agent. However, deployment of P. penetrans for this purpose is inhibited by a lack of understanding of its metabolism and the molecular mechanics underpinning parasitism of the host, in particular the initial attachment of the endospore to the nematode cuticle. Several attempts to assemble the genomes of species within this genus have been unsuccessful. Primarily this is due to the obligate parasitic nature of the bacterium which makes obtaining genomic DNA of sufficient quantity and quality which is free from contamination challenging. Taking advantage of recent developments in whole genome amplification, long read sequencing platforms, and assembly algorithms, we have developed a protocol to generate large quantities of high molecular weight genomic DNA from a small number of purified endospores. We demonstrate this method via genomic assembly of P. penetrans. This assembly reveals a reduced genome of 2.64Mbp estimated to represent 86% of the complete sequence; its reduced metabolism reflects widespread reliance on the host and possibly associated organisms. Additionally, apparent expansion of transposases and prediction of partial competence pathways suggest a high degree of genomic plasticity. Phylogenetic analysis places our sequence within the Bacilli, and most closely related to Thermoactinomyces species. Seventeen predicted BclA-like proteins are identified which may be involved in the determination of attachment specificity. This resource may be used to develop in vitro culture methods and to investigate the genetic and molecular basis of attachment specificity.

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