Purification and characterization of an outer membrane protein adhesin from Haemophilus parainfluenzae HP-28

A Uniquely Altered Oral Microbiome Composition Was Observed in Pregnant Rats With Porphyromonas gingivalis Induced Periodontal Disease

Porphyromonas gingivalis is an anaerobic bacterium commonly found in the oral cavity and associated with the development of periodontal disease. P. gingivalis has also been linked to several systemic vascular and inflammatory diseases including poor pregnancy outcomes. Little is known about the changes in the oral flora during pregnancy in connection to P. gingivalis infection. This pilot study aims to explore changes in the oral microbiome due to P. gingivalis inoculation and pregnancy in an in vivo rat model of periodontal disease. A metagenomic sequencing analysis targeting seven of the 16S rRNA gene variable regions was performed for oral samples collected at the following time points: baseline control (week 0), P. gingivalis inoculated (week 11), P. gingivalis inoculated and pregnant rat at necropsy (week 16). A second set of animals were also sampled to generate a sham-inoculated (week 11) control group. We found that the rat oral microbiome profiles were more similar to that of the human oral cavity compared to previous reports targeting one or two 16S variable regions. Overall, there appears to be a relatively stable core microbiome in the oral cavity. As expected, P. gingivalis induced periodontal disease resulted in oral microbiome dysbiosis. During pregnancy, some aspects of the oral microbiome shifted toward a more baseline-like profile. However, population analyses in terms of dissimilarity measures and especially metagenomic based predictions of select characteristics such as cell morphology, oxygen requirement, and major metabolite synthesis showed that pregnancy did not restore the composition of the oral microbiome. Rather, a uniquely altered oral microbiome composition was observed in pregnant rats with pre-established periodontal disease.

Microbial Diversity in the Early In Vivo-Formed Dental Biofilm

Although the mature dental biofilm composition is well studied, there is very little information on the earliest phase of in vivo tooth colonization. Progress in dental biofilm collection methodologies and techniques of large-scale microbial identification have made new studies in this field of oral biology feasible. The aim of this study was to characterize the temporal changes and diversity of the cultivable and noncultivable microbes in the early dental biofilm. Samples of early dental biofilm were collected from 11 healthy subjects at 0, 2, 4, and 6 h after removal of plaque and pellicle from tooth surfaces. With the semiquantitative Human Oral Microbiome Identification Microarray (HOMIM) technique, which is based on 16S rRNA sequence hybridizations, plaque samples were analyzed with the currently available 407 HOMIM microbial probes. This led to the identification of at least 92 species, with streptococci being the most abundant bacteria across all time points in all subjects. High-frequency detection was also made with Haemophilus parainfluenzae, Gemella haemolysans, Slackia exigua, and Rothia species. Abundance changes over time were noted for Streptococcus anginosus and Streptococcus intermedius (P = 0.02), Streptococcus mitis bv. 2 (P = 0.0002), Streptococcus oralis (P = 0.0002), Streptococcus cluster I (P = 0.003), G. haemolysans (P = 0.0005), and Stenotrophomonas maltophilia (P = 0.02). Among the currently uncultivable microbiota, eight phylotypes were detected in the early stages of biofilm formation, one belonging to the candidate bacterial division TM7, which has attracted attention due to its potential association with periodontal disease.

Mechanisms of adhesion by oral bacteria

Adherence to a surface is a key element for colonization of the human oral cavity by the more than 500 bacterial taxa recorded from oral samples. Three surfaces are available: teeth, epithelial mucosa, and the nascent surface created as each new bacterial cell binds to existing dental plaque. Oral bacteria exhibit specificity for their respective colonization sites. Such specificity is directed by adhesin-receptor cognate pairs on genetically distinct cells. Colonization is successful when adherent cells grow and metabolically participate in the oral bacterial community. The potential roles of adherence-relevant molecules are discussed in the context of the dynamic nature of the oral econiche.

Tissue distribution and developmental expression of type XVI collagen in the mouse

The expression of a recently identified collagen, alpha 1 (XVI), in adult mouse tissue and developing mouse embryo was examined by immunohistochemistry and in situ hybridization. A polyclonal antiserum was raised against a recombinant fusion protein, which contained a segment of 161 amino acids in the N-terminal noncollagenous domain of the human alpha 1 (XVI) collagen. Immunoprecipitation of metabolically labelled human or mouse fibroblast cell lysates with this antibody revealed a major, bacterial collagenase sensitive polypeptide of approximately 210 kDa. The size agrees with the prediction from the full-length cDNA. Immunofluorescence examination of adult mouse tissues using the affinity purified antibody revealed a rather broad distribution of the protein. The heart, kidney, intestine, ovary, testis, eye, arterial walls and smooth muscles all exhibited significant levels of expression, while the skeletal muscle, lung and brain showed very restricted and low signals. During development, no significant expression of the mRNA or protein was observed in embryo of day 8 of gestation, but strong signals was detected in placental trophoblasts. Expression in embryos was detectable first after day 11 of gestation with weak positive signals appearing in the heart. In later stages of development, stronger RNA hybridizations were observed in a variety of tissues, particularly in atrial and ventricular walls of the developing heart, spinal root neural fibers and skin. These data demonstrate that type XVI collagen represents another collagenous component widely distributed in the extracellular matrix and may contribute to the structural integrity of various tissues.

Human oral microbial ecology and dental caries and periodontal diseases

In the human oral cavity, which is an open growth system, bacteria must first adhere to a surface in order to be able to colonize. Ability to colonize a non-shedding tooth surface is necessary prior to any odontopathic or periodontopathic process. Complex microbe-host relationships occur and must be studied before the commensal-to-pathogenic nature of the human indigenous oral flora can be understood. Medical pathogens, if present in the appropriate host, always produce specific disease. Caries and periodontal diseases are conditional diseases, requiring numbers of certain indigenous species at various sites, particularly the tooth surface. In the case of caries, the condition is related to sugar consumption. Periodontal disease/s may require certain host and environmental conditions, such as local environment or nutritional factors in gingival crevicular fluids. Nonetheless, critical numbers of certain indigenous species must be present in order for these diseases to occur. The aim of this review is to understand the acquisition of the indigenous oral flora and the development of human dental plaque. The role of the salivary pellicle and adherence of indigenous bacteria to it are critical first steps in plaque development. Bacterial interactions with saliva, nutritional factors, growth factors, and microbial physiologic processes are all involved in the overall process of microbial colonization.

Cloning of the Streptococcus gordonii PK488 gene, encoding an adhesin which mediates coaggregation with Actinomyces naeslundii PK606

Coaggregation between Streptococcus gordonii PK488 and Actinomyces naeslundii PK606 is mediated by a 38-kDa streptococcal protein, designated ScaA. The gene, scaA, which encodes this protein has been cloned into Escherichia coli. A genomic S. gordonii PK488 library (in Lambda ZAP II) was screened with anti-S. gordonii immunoglobulin G absorbed with S. gordonii PK1804, an isogenic coaggregation-defective mutant of strain PK488. A positive recombinant phage was isolated, and a phagemid designated pRA1 was obtained which contained a 6.6-kb insert. Expression of scaA from pRA1 and from a subcloned internal 2.1-kb fragment was observed. The absorbed antiserum cross-reacted with a 34.7-kDa protein, SsaB, from S. sanguis 12, also a coaggregation partner of A. naeslundii PK606. Absorbed antiserum to S. gordonii PK488 and antiserum to SsaB both reacted with 38-kDa proteins in supernatants from mildly sonicated preparations from 11 other coaggregation partners of A. naeslundii PK606. Putative adhesin genes were identified in each of these coaggregation partners by Southern analysis of their genomic DNA with the cloned 2.1-kb fragment as a probe. A 30-base oligonucleotide probe based on the sequence of ssaB of S. sanguis 12 hybridized in an identical manner. These data extend the notion that most of the viridans streptococci that coaggregate with actinomyces are capable of expressing ScaA-related proteins.

Clustering of an outer membrane adhesin of Haemophilus parainfluenzae

Haemophilus parainfluenzae synthesizes an outer membrane protein adhesin which mediates binding to oral streptococci, salivary pellicle, and neuraminidase-treated erythrocytes. An indirect gold labeling technique and immunoelectron microscopy verified the location of this outer membrane protein. Further, a clustering of gold particles was observed in irregular patches at the cell surface.