Whole Genome Sequencing of First Janibacter indicus Isolate in China Revealed Three Unique Genomic Islands Compared with Saprophytic Strains

Introduction

Janibacter caused bacteriemia is one of the rare infections.

Methods

In the present study, we report the first isolation of Janibacter, a rare bacterial infection, from a bacteremia patient in China. Its 16S rDNA was amplified and designated as Janibacter YFY001, which belongs to J. indicus. In addition, its genome was sequenced through combined second- and third-generation genome sequencing methods.

Results

Based on its genome, we identified many virulence factors, such as catalase, gelatinase, FbpABC systems, and resistant genes, among others. Interestingly, three genomic islands were found in YFY001 by comparing its genome to environmental Janibacter strains.

Discussion

Our study not only provides the necessary genomic information for in-depth study of Janibacter, but also provides a novel methodology for studying future cases of rare bacterial infection.

Complete genome sequence of Janibaecter indicus YB324 from an Atlantic marine sediment

Janibacter indicus YB324, a gram-positive, aerobic and non-motile actinobacterium isolated from south Atlantic sediment at a depth of 2875 m. The complete genome sequence of the strain YB324 was obtained using PacBio Sequel HGAP.4 and comprised of 3,369,845 base pairs with a 71.3 mol% G + C content, 3225 protein-coding genes, 53 RNAs. In silico analysis confirmed the genes associated with polysaccharide hydrolyzation, nitrite reduction, and phenol degradation. Multiple natural product biosynthesis gene clusters were identified as well. The complete genome sequence will provide insight into the potential use of this strain in biotechnological and natural product biosynthesis applications.

Marine Rare Actinomycetes: A Promising Source of Structurally Diverse and Unique Novel Natural Products

Rare actinomycetes are prolific in the marine environment; however, knowledge about their diversity, distribution and biochemistry is limited. Marine rare actinomycetes represent a rather untapped source of chemically diverse secondary metabolites and novel bioactive compounds. In this review, we aim to summarize the present knowledge on the isolation, diversity, distribution and natural product discovery of marine rare actinomycetes reported from mid-2013 to 2017. A total of 97 new species, representing 9 novel genera and belonging to 27 families of marine rare actinomycetes have been reported, with the highest numbers of novel isolates from the families Pseudonocardiaceae, Demequinaceae, Micromonosporaceae and Nocardioidaceae. Additionally, this study reviewed 167 new bioactive compounds produced by 58 different rare actinomycete species representing 24 genera. Most of the compounds produced by the marine rare actinomycetes present antibacterial, antifungal, antiparasitic, anticancer or antimalarial activities. The highest numbers of natural products were derived from the genera Nocardiopsis, Micromonospora, Salinispora and Pseudonocardia. Members of the genus Micromonospora were revealed to be the richest source of chemically diverse and unique bioactive natural products.

Description of Janibacter massiliensis sp. nov., cultured from the vaginal discharge of a patient with bacterial vaginosis

Strain Marseille-P4121^T was isolated from a vaginal sample of a 45-year-old French woman with bacterial vaginosis. It is a Gram-positive, asporogenous, non-motile and aerobic bacterium. Strain Marseille-P4121^T exhibits 98.2% 16S rRNA sequence similarity with Janibacter alkaliphilus strain SCSIO 10480^T, a phylogenetically closely related species with standing in nomenclature. Its major fatty acids were identified as C_18:1ω9 (34.4%), C_16:0 (30.1%), and C_18:0 (19%). The draft genome size of strain Marseille-P4121^T is 2,452,608 bp long with a 72.5% G+C content and contains 2351 protein-coding genes and 49 RNA genes including 3 rRNA genes. We propose that strain Marseille-P4121^T (= CECT 9671^T = CSUR P4121^T) is the type strain of the new species Janibacter massiliensis sp. nov.

Genome-Based Taxonomic Classification of the Phylum Actinobacteria

The application of phylogenetic taxonomic procedures led to improvements in the classification of bacteria assigned to the phylum Actinobacteria but even so there remains a need to further clarify relationships within a taxon that encompasses organisms of agricultural, biotechnological, clinical, and ecological importance. Classification of the morphologically diverse bacteria belonging to this large phylum based on a limited number of features has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees. Here, draft genome sequences of a large collection of actinobacterial type strains were used to infer phylogenetic trees from genome-scale data using principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families, and genera, as well as many species and a few subspecies were shown to be in need of revision leading to proposals for the recognition of 2 orders, 10 families, and 17 genera, as well as the transfer of over 100 species to other genera. In addition, emended descriptions are given for many species mainly involving the addition of data on genome size and DNA G+C content, the former can be considered to be a valuable taxonomic marker in actinobacterial systematics. Many of the incongruities detected when the results of the present study were compared with existing classifications had been recognized from 16S rRNA gene trees though whole-genome phylogenies proved to be much better resolved. The few significant incongruities found between 16S/23S rRNA and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences. Similarly good congruence was found between the discontinuous distribution of phenotypic properties and taxa delineated in the phylogenetic trees though diverse non-monophyletic taxa appeared to be based on the use of plesiomorphic character states as diagnostic features.

Untapped bacterial diversity and metabolic potential within Unkeshwar hot springs, India

Hot springs support diverse and interesting groups of microorganisms adapted to extreme conditions and gaining attention in biotechnological applications. However, due to limitations of cultivation methods, a majority of such extremophiles remain uncultivated and unexplored. The advent of multiple cultivation conditions and specialized culture media could possibly aid to access the unexplored microbial portion of hot springs. In the present study, different media and isolation strategies were applied to isolate hitherto unexplored bacterial taxa in the water samples collected from Unkeshwar hot springs, India. Molecular, phylogenetic and predictive functional characterization of the isolated bacterial population was done using 16S rRNA sequencing coupled with Tax4Fun tools. Furthermore, representative isolates were screened for important enzymes (cellulase, xylanase, amylase, and protease) and heavy metal tolerance (chromium, arsenic) properties. A total of 454 bacterial isolates obtained were mapped into 57 unique bacterial genera and 4 different bacterial phyla. Interestingly, 37 genera not previously isolated from Indian hot springs, were isolated for the first time in the present study. However, most of these genera (23 out of 37) were reported only in metagenomics studies from Indian and global hot springs. Furthermore, around 14 genera not previously cultivated and not detected in metagenomics studies of hot springs are documented here. The metabolic potential was ascertained by determining the abundance of specific genes using in silico based Tax4Fun tool, which identified around 315 metabolic pathways for metabolism of carbohydrates, synthesis of secondary metabolites and degradation of xenobiotic compounds. Bioprospection study revealed that 33 and 25 bacterial genera were positive for enzyme production and resistance to the heavy metals, respectively. The present study revealed the advantages of cultivation methods using a comprehensive multiple isolation approach for exploring untapped and unique bacterial diversity, and also utilities for various biotechnological and environmental applications.

First case of bacteremia caused by Janibacter hoylei

Janibacter hoylei has previously been isolated only from an air sample in the upper atmosphere and clinical significance of J. hoylei was not yet established. Herein, we report a case of bacteremia caused by J. hoylei. An 8-week-old previously healthy male infant presented to the emergency room with fever. Blood culture yielded growth of Gram-positive bacilli and this microorganism could not be identified with conventional phenotypic methods. The isolate was identified by 16S rRNA gene sequencing, and the patient was successfully treated with vancomycin. To our knowledge, this is the first report of the recovery of J. hoylei in humans. This case shows that J. hoylei can be a potential pathogen in young children.