Haemophilus parainfluenzae expresses diverse lipopolysaccharide O-antigens using ABC transporter and Wzy polymerase-dependent mechanisms

Exploring Competitive Relationship Between Haemophilus parainfluenzae and Mitis Streptococci via Co-Culture-Based Molecular Diagnosis and Metabolomic Assay

Various bacterial strains with nitrate-reducing capacity (NRC), such as Haemophilus, Actinomyces, and Neisseria, are known to promote NH3 production, control pH in the oral cavity, and inhibit the growth of aciduric bacteria. However, experimental evidence on various estimated bacterial networks within the salivary microbiome is insufficient. This study aims to explore potential bacterial compositional competition observed within saliva samples from dental caries patients through a co-culture assay of mitis Streptococci, which is a primary colonizer in the salivary microbiome, and nitrate-reducing bacteria Haemophilus parainfluenzae. We investigated bacterial growth efficiency change by co-culture time using the qRT-PCR method. In addition, we applied LC/Q-TOF-based metabolites screening to confirm metabolic interactions between oral bacterial species and their association with dental caries from a metabolomics perspective. As a result, we first found that the nitrate reduction ability of H. parainfluenzae is maintained even in a co-culture environment with the mitis Streptococci group through a nitrate reduction test. However, nitrate reduction efficiency was hindered when compared with monoculture-based nitrate reduction test results. Next, we designed species-specific primers, and we confirmed by qRT-PCR that there is an obvious competitive relationship in growth efficiency between H. parainfluenzae and two mitis Streptococci (S. australis and S. sanguinis). Furthermore, although direct effects of nitrate reduction on competition have not been identified, we have potentially confirmed through LC/Q-TOF-based metabolite screening analysis that the interaction of various metabolic compounds synthesized from mitis Streptococci is driving inter-strain competition. In particular, we constructed a basic reference core-metabolites list to understand the metabolic network between each target bacterial species (H. parainfluenzae and mitis Streptococci) within the salivary microbiome, which still lacks accumulated research data. Ultimately, we suggest that our data have potential value to be referenced in further metagenomics and metabolomics-based studies related to oral health care.

Microbiological characteristics of different tongue coatings in adults

Background

Tongue coating is an important health indicator in traditional Chinese medicine (TCM). The tongue coating microbiome can distinguish disease patients from healthy controls. To study the relationship between different types of tongue coatings and health, we analyzed the species composition of different types of tongue coatings and the co-occurrence relationships between microorganisms in Chinese adults.

From June 2019 to October 2020, 158 adults from Hangzhou and Shaoxing City, Zhejiang Province, were enrolled. We classified the TCM tongue coatings into four different types: thin white tongue fur (TWF), thin yellow tongue fur (TYF), white greasy tongue fur (WGF), and yellow greasy tongue fur (YGF). Tongue coating specimens were collected and used for 16S rRNA gene sequencing using the Illumina MiSeq system. Wilcoxon rank-sum and permutational multivariate analysis of variance tests were used to analyze the data. The microbial networks in the four types of tongue coatings were inferred independently using sparse inverse covariance estimation for ecological association inference.

Results

The microbial composition was similar among the different tongue coatings; however, the abundance of microorganisms differed. TWF had a higher abundance of Fusobacterium periodonticum and Neisseria mucosa, the highest α-diversity, and a highly connected community (average degree = 3.59, average closeness centrality = 0.33). TYF had the lowest α-diversity, but the most species in the co-occurrence network diagram (number of nodes = 88). The platelet-to-lymphocyte ratio (PLR) was associated with tongue coating (P = 0.035), and the YGF and TYF groups had higher PLR values. In the co-occurrence network, Aggregatibacter segnis was the “driver species” of the TWF and TYF groups and correlated with C-reactive protein (P < 0.05). Streptococcus anginosus was the “driver species” in the YGF and TWF groups and was positively correlated with body mass index and weight (P < 0.05).

Conclusion

Different tongue coatings have similar microbial compositions but different abundances of certain bacteria. The co-occurrence of microorganisms in the different tongue coatings also varies. The significance of different tongue coatings in TCM theory is consistent with the characteristics and roles of the corresponding tongue-coating microbes. This further supports considering tongue coating as a risk factor for disease.

Genome Structure of the Opportunistic Pathogen Paracoccus yeei (Alphaproteobacteria) and Identification of Putative Virulence Factors

Bacteria of the genus Paracoccus are common components of the microbiomes of many naturally- and anthropogenically shaped environments. One species, Paracoccus yeei, is unique within the genus because it is associated with opportunistic human infections. Therefore, strains of P. yeei may serve as an interesting model to study the transition from a saprophytic to a pathogenic lifestyle in environmental bacteria. Unfortunately, knowledge concerning the biology, genetics and genomic content of P. yeei is fragmentary; also the mechanisms of pathogenicity of this bacterium remain unclear. In this study we provide the first insight into the genome composition and metabolic potential of a clinical isolate, P. yeei CCUG 32053. This strain has a multipartite genome (4,632,079 bp) composed of a circular chromosome plus eight extrachromosomal replicons pYEE1–8: 3 chromids and 5 plasmids, with a total size of 1,247,173 bp. The genome has been significantly shaped by the acquisition of genomic islands, prophages (Myoviridae and Siphoviridae phage families) and numerous insertion sequences (ISs) representing seven IS families. Detailed comparative analysis with other complete genomic sequences of Paracoccus spp. (including P. yeei FDAARGOS_252 and TT13, as well as non-pathogenic strains of other species in this genus) enabled us to identify P. yeei species-specific genes and to predict putative determinants of virulence. This is the first attempt to identify pathoadaptive genetic information of P. yeei and to estimate the role of the mobilome in the evolution of pathogenicity in this species.

Haemophilus parainfluenzae Strain ATCC 33392 Forms Biofilms In Vitro and during Experimental Otitis Media Infections

Haemophilus parainfluenzae is a nutritionally fastidious, Gram-negative bacterium with an oropharyngeal/nasopharyngeal carriage niche that is associated with a range of opportunistic infections, including infectious endocarditis and otitis media (OM). These infections are often chronic/recurrent in nature and typically involve bacterial persistence within biofilm communities that are highly resistant to host clearance. This study addresses the primary hypothesis that H. parainfluenzae forms biofilm communities that are important determinants of persistence in vivo The results from in vitro biofilm studies confirmed that H. parainfluenzae formed biofilm communities within which the polymeric matrix was mainly composed of extracellular DNA and proteins. Using a chinchilla OM infection model, we demonstrated that H. parainfluenzae formed surface-associated biofilm communities containing bacterial and host components that included neutrophil extracellular trap (NET) structures and that the bacteria mainly persisted in these biofilm communities. We also used this model to examine the possible interaction between H. parainfluenzae and its close relative Haemophilus influenzae, which is also commonly carried within the same host environments and can cause OM. The results showed that coinfection with H. influenzae promoted clearance of H. parainfluenzae from biofilm communities during OM infection. The underlying mechanisms for bacterial persistence and biofilm formation by H. parainfluenzae and knowledge about the survival defects of H. parainfluenzae during coinfection with H. influenzae are topics for future work.