Publications

4539

Abstract Background Candidatus Ornithobacterium hominis (O. hominis), which was identified in nasopharyngeal swabs from Egypt, has been associated with respiratory disorders in humans. O. hominis, a recently identified member of the Flavobacteriaceae family, belongs to the largest family within the Bacteroidetes phylum. This family includes hundreds of species and 90 genera, including major human pathogens such as Capnocytophaga canimorsus and Elizabethkingia meningoseptica. Herein, we presented two draft genome assemblies of O. hominis that were extracted from metagenomic data using the Illumina sequencing method. The alignment of reads against the O. hominis genome was accomplished using BLASTN, and the reads with significant hits were extracted using Seqtk and assembled using SPAdes. The primary goal of this study was to obtain a more profound understanding of the genomic landscape of O. hominis, with an emphasis on identifying the associated virulence, antimicrobial genes, and distinct defense mechanisms to shed light on the potential role of O. hominis in human respiratory infections. Results The genome size was estimated to be 1.84 Mb, including 1,931,660 base pairs (bp), with 1,837 predicted coding regions and a G+C content of 35.62%. Genes encoding gliding motility, antibiotic resistance (20 genes), and the toxA gene were all included in the genome assembly. Gliding motility lipoproteins (GldD, GldJ, GldN, and GldH) and the gliding motility-associated ABC transporter substrate-binding protein, which acts as a crucial virulence mechanism in Flavobacterium species, were identified. The genome contained unique genes encoding proteins, such as the ParE1 toxin that defend against the actions of quinolone and other antibiotics. The cobalt-zinc-cadmium resistance gene encoding the protein CzcB, which is necessary for metal resistance, urease regulation, and colonization, was also detected. Several multidrug resistance genes encoding proteins were identified, such as MexB, MdtK, YheI, and VanC. Conclusion Our study focused on identifying virulence factors, and antimicrobial resistance genes present in the core genome of O. hominis. These findings provide valuable insights into the potential pathogenicity and antibiotic susceptibility of O. hominis.

Ticks are important vectors of zoonotic diseases and play a major role in the circulation and transmission of many rickettsial species. The aim of this study was to investigate the carriage of Candidatus Rickettsia tarasevichiae (CRT) in a total of 1168 ticks collected in Inner Mongolia to elucidate the potential public health risk of this pathogen, provide a basis for infectious disease prevention, control and prediction and contribute diagnostic ideas for clinical diseases that present with fever in populations exposed to ticks. A total of four tick species, Haemaphysalis concinna (n = 21), Dermacentor nuttalli (n = 122), Hyalomma marginatum (n = 148), and Ixodes persulcatus (n = 877), were collected at nine sampling sites in Inner Mongolia, China, and identified by morphological and molecular biological methods. Reverse transcription PCR targeting the 16S ribosomal RNA (rrs), gltA, groEL, ompB and Sca4 genes was used to detect CRT DNA. Sequencing was used for pathogen species confirmation. The molecular epidemiological analysis showed that three species of ticks were infected with CRT, and the overall positive rate was as high as 42%. The positive rate of I. persulcatus collected in Hinggan League city was up to 96%, and that of I. persulcatus collected in Hulun Buir city was 50%. The pool positive rates of D. nuttalli and H. marginatum collected in Bayan Nur city and H. concinna collected in Hulun Buir city were 0%, 28% and 40%, respectively. This study revealed the high prevalence of CRT infection in ticks from Inner Mongolia and the first confirmation of CRT detected in H. marginatum in China. The wide host range and high infection rate in Inner Mongolia may dramatically increase the exposure of CRT to humans and other vertebrates. The role of H. marginatum in the transmission of rickettsiosis and its potential risk to public health should be further considered.

The digestive organs of terrestrial isopods harbour bacteria of the recently proposed mollicute family Hepatoplasmataceae. The only complete genome available so far for Hepatoplasmataceae is that of ‘Candidatus Hepatoplasma crinochetorum’. The scarcity of genome sequences has hampered our understanding of the symbiotic relationship between isopods and mollicutes. Here, we present four complete metagenome-assembled genomes (MAGs) of uncultured Hepatoplasmataceae members identified from shotgun sequencing data of isopods. We propose genomospecies names for three MAGs that show substantial sequence divergence from any previously known Hepatoplamsataceae members: ‘Candidatus Tyloplasma litorale’ identified from the semiterrestrial isopod Tylos granuliferus, ‘Candidatus Hepatoplasma vulgare’ identified from the common pill bug Armadillidium vulgare, and ‘Candidatus Hepatoplasma scabrum’ identified from the common rough woodlouse Porcellio scaber. Phylogenomic analysis of 155 mollicutes confirmed that Hepatoplasmataceae is a sister clade of Metamycoplasmataceae in the order Mycoplasmoidales. The 16S ribosomal RNA gene sequences and phylogenomic analysis showed that ‘Candidatus Tyloplasma litorale’ and other semiterrestrial isopod-associated mollicutes represent the placeholder genus ‘g_Bg2’ in the r214 release of the Genome Taxonomy Database, warranting their assignment to a novel genus. Our analysis also revealed that Hepatoplasmataceae lack major metabolic pathways but has a likely intact type IIA CRISPR-Cas9 machinery. Although the localization of the Hepatoplasmatacae members have not been verified microscopically in this study, these genomic characteristics are compatible with the idea that these mollicutes have an ectosymbiotic lifestyle with high nutritional dependence on their host, as has been demonstrated for other members of the family. We could not find evidence that Hepatoplasmataceae encode polysaccharide-degrading enzymes that aid host digestion. If they are to provide nutritional benefits, it may be through extra-copy nucleases, peptidases, and a patatin-like lipase. Exploration of potential host-symbiont interaction-associated genes revealed large, repetitive open reading frames harbouring beta-sandwich domains, possibly involved with host cell adhesion. Overall, genomic analyses suggest that isopod-mollicute symbiosis is not characterized by carbohydrate degradation, and we speculate on their potential role as defensive symbionts through spatial competition with pathogens to prevent infection.