Novel anti-herpes simplex activity of Chryseobacterium indologenes: Genomic and metabolomic insights

Herpes simplex virus (HSV) is a pathogenic virus responsible for various diseases, necessitating alternative antiviral strategies for HSV-1 treatment. Given the antiviral properties of lactic acid (LA), we screened rhizobacteria from the maize (Zea mays L.) rhizosphere for organic acid production. Among the isolates, SR50, SR126, and SR135 exhibited significant LA production, confirmed by High-Performance Liquid Chromatography (HPLC) analysis. Their antiviral efficacy against HSV-1 was evaluated by determining IC50 values and selectivity indices (SI = CC50/IC50), with SR50, SR126, and SR135 displaying SI values of 135.14, 10.74, and 2.17, respectively. SR50, identified via 16S rRNA sequencing as Chryseobacterium indologenes, was selected for further antiviral analysis. The cell-free supernatant (CFS) of SR50 demonstrated 73.3 % inhibition of viral adsorption, 60 % virucidal activity, and a 46.7 % reduction in viral replication. Metabolomic profiling using Gas Chromatography-Mass Spectrometry (GC-MS) identified short- and long-chain organic fatty acids. Whole Genome Sequencing (WGS) revealed a 4,581,372 bp genome encoding diverse biosynthetic pathways, including siderophores, plant hormones, terpenoids, polyketides, and other bacterial secondary metabolites. Additionally, genes encoding lactaldehyde dehydrogenase and pyruvate dehydrogenase confirmed the presence of lactic and acetic acid biosynthesis pathways. This study presents the first report of C. indologenes SR50 exhibiting anti-HSV-1 activity, highlighting its potential as a novel antiviral resource.

Flavobacterium plantiphilum sp. nov., Flavobacterium rhizophilum sp. nov., Flavobacterium rhizosphaerae sp. nov., Chryseobacterium terrae sp. nov., and Sphingomonas plantiphila sp. nov. isolated from salty soil showing plant growth promoting potential

Members of the genera Flavobacterium, Chryseobacterium and Sphingomonas constitute a group of microorganisms in the rhizosphere associated with plant growth promoting (PGP) features. A polyphasic approach was employed to ascertain the taxonomic status of five selected strains. Overall genome relatedness indices of digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) between the strains and the other members of the genera Flavobacterium, Chryseobacterium and Sphingomonas were found to be below the established thresholds, respectively. Morphological, physiological, and biochemical characteristics of the strains confirmed their status as five novel species. A large variety of genes involved in plant growth promotion and carbohydrate utilization were found in all strains suggesting a contribution of all strains to PGP. Based on the result of the polyphasic characterization, the following names are proposed: Chryseobacterium terrae sp. nov., with the strain ST-37T as the type strain (= CCM 9260T = LMG 32728T); Flavobacterium plantiphilum sp. nov., with the strain ST-87T as the type strain CIP 112180T = DSM 114790T = LMG 32757T); Flavobacterium rhizophilum sp. nov., with the strain ST-75T as the type strain (= CIP 112185T = DSM 114831T = LMG 32758T); Flavobacterium rhizosphaerae sp. nov., with the strain ST-119T as the type strain (CIP 112181T = DSM 114832T = LMG 32756T); and Sphingomonas plantiphila sp. nov. with the strain ST-64 T as the type strain (= CCM 9261T = CIP 112178T = DSM 114515T = LMG 32729T).

Comparative Lipidomics of Oral Commensal and Opportunistic Bacteria

The oral cavity contains a vast array of microbes that contribute to the balance between oral health and disease. In addition, oral bacteria can gain access to the circulation and contribute to other diseases and chronic conditions. There are a limited number of publications available regarding the comparative lipidomics of oral bacteria and fungi involved in the construction of oral biofilms, hence our decision to study the lipidomics of representative oral bacteria and a fungus. We performed high-resolution mass spectrometric analyses (<2.0 ppm mass error) of the lipidomes from five Gram-positive commensal bacteria: Streptococcus oralis, Streptococcus intermedius, Streptococcus mitis, Streptococcus sanguinis, and Streptococcus gordonii; five Gram-positive opportunistic bacteria: Streptococcus mutans, Staphylococcus epidermis, Streptococcus acidominimus, Actinomyces viscosus, and Nanosynbacter lyticus; seven Gram-negative opportunistic bacteria: Porphyromonas gingivalis. Prevotella brevis, Proteus vulgaris, Fusobacterium nucleatum, Veillonella parvula, Treponema denticola, and Alkermansia muciniphila; and one fungus: Candida albicans. Our mass spectrometric analytical platform allowed for a detailed evaluation of the many structural modifications made by microbes for the three major lipid scaffolds: glycerol, sphingosine and fatty acyls of hydroxy fatty acids (FAHFAs).

Kaistella rhinocerotis sp. nov., isolated from the faeces of rhinoceros and reclassification of Chryseobacterium faecale as Kaistella faecalis comb. nov

Strain Ran72T, a novel Gram-stain-negative, obligately aerobic, non-motile, and rod-shaped bacterium, was isolated from the faeces of the rhinoceros species Ceratotherium simum. The novel bacterial strain grew optimally in Reasoner's 2A medium under the following conditions: 0 % (w/v) NaCl, pH 7.5, and 30 °C. Based on phylogenetic analysis using 16S rRNA gene sequencing, strain Ran72T was found to be most closely related to Chryseobacterium faecale F4T (98.4 %), Kaistella soli DKR-2T (98.0 %), and Kaistella haifensis H38T (97.4 %). A comprehensive genome-level comparison between strain Ran72T with C. faecale F4T, K. soli DKR-2T, and K. haifensis H38T revealed average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity values of ≤74.9, ≤19.3, and ≤78.7 %, respectively. The major fatty acids were anteiso-C15 : 0 (22.3 %), with MK-6 being the predominant respiratory quinone. The major polar lipids of strain Ran72T were phosphatidylethanolamine, four unidentified aminolipids, and two unidentified lipids. Based on our chemotaxonomic, genotypic, and phenotype characterizations, strain Ran72T was identified as representing a novel species in the genus Kaistella, for which the name Kaistella rhinocerotis sp. nov. is proposed, with the type strain Ran72T (=KACC 23136T=JCM 36038T). Based on the outcomes of our phylogenomic study, Chryseobacterium faecale should be reclassified under the genus Kaistella as Kaistella faecalis comb. nov.

Circular genomes of two bacterial strains capable of growing in a CO2-containing atmosphere

The bacterial strains Brochothrix thermosphacta DH-B18 and Rathayibacter sp. DH-RSZ4 were isolated from raw sausage and escalope samples and grown in a CO2-rich modified atmosphere. Here, we present both circular genomes obtained by nanopore sequencing.