No abstract

A Gram-stain-negative, facultatively anaerobic, rod-shaped, non-flagellated and non-gliding bacterium, designated strain B011, was isolated from marine algae Gracilaria blodgettii collected from the coast of Lingshui county, Hainan, China. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain B011, Seonamhaeicola algicola (96.8 % 16S rRNA gene sequence similarity) and Seonamhaeicola aphaedonensis (95.0 %) belonged to the same clade. Optimal growth occurred in the presence of 3.0 % (w/v) NaCl, at pH 6.5-7.5 and at 28 °C. Menaquinone-6 (MK-6) was the predominant respiratory quinone. The major fatty acids (>10 %) were iso-C15 : 1 G (23.4 %) and iso-C15 : 0 (22.8 %). The major polar lipids were phosphatidylethanolamine, one aminolipid and three unknown lipids. The DNA G+C content of strain B011 was 33.9 mol%. On the basis of polyphasic analysis, strain B011 is considered to represent a novel species in the genus Seonamhaeicola, for which the name Seonamhaeicolamarinus sp. nov. is proposed. The type strain is B011 (=MCCC 1H00146=NBRC 112333).

Multidrug-resistant (MDR) Acinetobacter baumannii is a critical threat to human health globally. We constructed a genome-scale metabolic model iAB5075 for the hypervirulent, MDR A. baumannii strain AB5075. Predictions of nutrient utilization and gene essentiality were validated using Biolog assay and a transposon mutant library. In vivo transcriptomics data were integrated with iAB5075 to elucidate bacterial metabolic responses to the host environment. iAB5075 contains 1530 metabolites, 2229 reactions, and 1015 genes, and demonstrated high accuracies in predicting nutrient utilization and gene essentiality. At 4 h post-infection, a total of 146 metabolic fluxes were increased and 52 were decreased compared to 2 h post-infection; these included enhanced fluxes through peptidoglycan and lipopolysaccharide biosynthesis, tricarboxylic cycle, gluconeogenesis, nucleotide and fatty acid biosynthesis, and altered fluxes in amino acid metabolism. These flux changes indicate that the induced central metabolism, energy production, and cell membrane biogenesis played key roles in establishing and enhancing A. baumannii bloodstream infection. This study is the first to employ genome-scale metabolic modeling to investigate A. baumannii infection in vivo. Our findings provide important mechanistic insights into the adaption of A. baumannii to the host environment and thus will contribute to the development of new therapeutic agents against this problematic pathogen.

Short tandem repeats (STRs) are highly informative genetic markers that have been used extensively in population genetics analysis. They are an important source of genetic diversity and can also have functional impact. Despite the availability of bioinformatic methods that permit large-scale genome-wide genotyping of STRs from whole genome sequencing data, they have not previously been applied to sequencing data from large collections of malaria parasite field samples. Here, we have genotyped STRs using HipSTR in more than 3,000 Plasmodium falciparum and 174 Plasmodium vivax published whole-genome sequence data from samples collected across the globe. High levels of noise and variability in the resultant callset necessitated the development of a novel method for quality control of STR genotype calls. A set of high-quality STR loci (6,768 from P. falciparum and 3,496 from P. vivax) were used to study Plasmodium genetic diversity, population structures and genomic signatures of selection and these were compared to genome-wide single nucleotide polymorphism (SNP) genotyping data. In addition, the genome-wide information about genetic variation and other characteristics of STRs in P. falciparum and P. vivax have been available in an interactive web-based R Shiny application PlasmoSTR (https://github.com/bahlolab/PlasmoSTR).