See-Too, W.-S. | Search bioRxiv

bioRxiv2020

Oecophyllibacter saccharovorans gen. nov. sp. nov., a bacterial symbiont of the weaver ant Oecophylla smaragdina with a plasmid-borne sole rrn operon

In this study, bacterial strains Ha5T, Ta1 and Jb2 were isolated from different colonies of weaver ant Oecophylla smaragdina. They were distinguished as different strains based on matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and distinctive random-amplified polymorphic DNA (RAPD) fingerprints. Cells of these bacterial strains were Gram-negative, rod-shaped, aerobic, non-motile, catalase-positive and oxidase-negative. They were able to grow at 15-37{degrees}C (optimum, 28-30{degrees}C) and in the presence of 0-1.5 % (w/v) NaCl (optimum 0%). Their predominant cellular fatty acids were C18:1{omega} 7c, C16:0, C19:0{omega} 8c cyclo, C14:0 and C16:0 2-OH. Strains Ha5T, Ta1 and Jb2 shared highest 16S rRNA gene sequence similarity (94.56-94.63%) with Neokomagataea tanensis NBRC106556T but were phylogenetically closer to Bombella spp. and Saccharibacterfloricola DSM15669T. Both 16S rRNA gene sequence-based phylogenetic analysis and core gene-based phylogenomic analysis placed them in a distinct lineage in family Acetobacteraceae. These bacterial strains shared higher than species level thresholds in multiple overall genome-relatedness indices which indicated that they belonged to the same species. In addition, they did not belong to any of the current taxa of Acetobacteraceae as they had low pairwise average nucleotide identity ([≤]70.7%), in silico DNA-DNA hybridization ([≤]39.5%) and average amino acid identity ([≤]66.u%) values with all the type members of the family. Based on these results, bacterial strains Ha5T, Ta1 and Jb2 represent a novel species of a novel genus in family Acetobacteraceae, for which we propose the name Oecophyllibacter saccharovorans gen. nov. sp. nov., and strain Ha5T as the type strain.

microbiology↗

bioRxiv2019

Characterisation of Quorum Sensing System and Its Role in Global Regulation in Hafnia alvei

Quorum sensing (QS) is a regulatory process achieved via cell-to-cell communication that involves release and detection of autoinducers (AIs), and which occurs in a wide range of bacteria. To date, QS has been associated to events of pathogenesis, biofilm formation, and antibiotic resistance in clinical, industrial, and agricultural contexts. The main objective of this study was to characterise the role of N-Acyl homoserine lactone (AHL) type QS in Hafnia alvei FB1, a bacterial strain isolated from frozen vacuum-packed fish paste meatballs, via identification of QS core genes using a genomic approach, followed by comparative transcriptomic profiling between QS-deficient mutants and wild-type strains. H. alvei FB1 is known to produce two types of AHLs, namely, N-(3-oxohexanoyl) homoserine lactone (3OC6-HSL) and N-(3-oxooctanoyl) homoserine lactone (3OC8-HSL). The complete genome sequence of strain FB1 was obtained and a single gene for AHL synthase (halI) and its cognate receptor (halR) were identified. QS-deficient mutants of FB1 were constructed via the {lambda}-Red recombineering method. Removal of the QS genes in strain FB1 affected mainly mechanisms in cell division and nutrient uptake, as well as resistance to a number of antibiotics, which are crucial for survival, adaptation and colonisation of both food and the host gut environment. Impact statementThe Hafnia genus is known as opportunistic pathogen in both nosocomial and community-acquired infections, however, involvement and mechanism of pathogenesis of Hafnia in infection diseases is uncertain. We investigate the role of the signalling molecule, N-acyl homoserine lactones (AHLs), in a Hafnia alvei strain, since AHLs play important roles in pathogenicity, survival or adaptation in other pathogen. This comparative transciptomic study has revealed that AHLs are involved in mechanisms in cell division and nutrient uptake, as well as resistance to a number of antibiotics, which are crucial for survival, adaptation and colonisation of both food and the host gut environment. This finding provides insight and possible strategy to combat this opportunistic pathogen. Data summaryGenome sequence is deposited in NCBI GenBank under accession number CP009706. The transcriptomic data, have been deposited in the Gene Expression Omnibus (GEO) database (https://www.ncbi.nlm.nih.gov/gds) under accession number GSE93000.

genomics↗