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Factors Controlling the Microflora of the Healthy Mouth
Published in Michael J. Hill, Philip D. Marsh, Human Microbial Ecology, 2020
Actinobacillus actinomycetemcomitans has attracted much attention in recent years as an important organism in the etiology of some forms of periodontal disease. Its uncertain taxonomic position is therefore a great disadvantage. It has been proposed to reassign A. actinomycetemcomitans to the genus Haemophilus as H. actinomycetemcomitans due to its homology with H. aphrophilus, and lack of similarity to other Actinobacillus species.74 The dissimilarity between A. actinomycetemcomitans and the type species, H. influenzae, however, makes this reassignment problematical. The solution may be to propose a new genus for A. actinomycetemcomitans, H. aphrophilus, and H. paraphrophilus. Capnocytophaga is a relatively new genus of CO2-dependent, Gram-negative rods with gliding motility found in gingival plaque. It comprises three species, namely C. gingivalis, C. ochracea, and C. sputigena.75Differentiation of these species on the basis of simple tests for phenotypical characteristics is, however, not possible at present.76
Progress in Antimalarial Drug Discovery and Development
Published in Venkatesan Jayaprakash, Daniele Castagnolo, Yusuf Özkay, Medicinal Chemistry of Neglected and Tropical Diseases, 2019
Anna C.C. Aguiar, Wilian A. Cortopassi, Antoniana U. Krettli
Plasmodium spp parasites have a complex life cycle, which initiates when highly motile sporozoite forms are inoculated into the dermis of the mammalian host during the mosquito bite (Figure 3). A proportion of the parasites enters blood capillaries, relying on gliding motility, a random process enabling them to reach and penetrate blood vessels in the bloodstream (Frenal et al. 2017). Other sporozoites are drained in the lymphatic system and reach the lymph node where most are degraded by dendritic leucocytes. Some sporozoites partially differentiate into exoerythrocytic stages in the skin (Amino et al. 2008). The parasites migrating through Kupffer cells avoid phagocytosis by these resident macrophages and are retained in hepatocytes, then differentiate and divide thereby originating thousands of new cells, the merozoits (Tavares et al. 2013). The migration through the hepatocytes is an essential step of the Plasmodium life cycle, after exocytosis of the sporozoite apical organelles, a prerequisite for infection (Mota et al. 2001). In addition, prior to hepatocyte invasion, the sporozoites must leave the circumsporozoite (CSP), a multifunctional protein that is involved in the mosquitoes’ sporogonic cycle, including invasion of the salivary glands. The specific arrest of sporozoites in the liver sinusoid depends on their gliding motility and the hepatocyte recognition and entry (Sultan 1999).
The Parasite's Way of life
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2015
Eric S. Loker, Bruce V. Hofkin
Less motile protozoan parasites often find their target tissue as a consequence of an affinity between certain molecules on the parasite surface and other molecules found on the membrane of the target tissue. We saw earlier in this chapter, for example, that the initial round of replication by Toxoplasma gondii in gut epithelial cells of the intermediate host is followed by invasion of phagocytic cells. These phagocytic cells leave the intestine and effectively disseminate the parasite throughout the host’s body. Like other apicomplexans, T. gondii has adhesion proteins associated with its plasma membrane. The attachment between a T. gondii merozoite and a phagocytic cell occurs when the parasite adhesion protein, called mic2, binds to ICAM-1 on the surface of the phagocytic cell. The parasite then penetrates the phagocytic cell using gliding motility, a mode of locomotion unique to the apicomplexans. This type of movement occurs only on substrates and in the absence of locomotory organelles and involves the interaction of the parasite surface proteins with actinomyosin found beneath the parasite cell membrane in the cytoskeleton. In effect, the myosin motor proteins moving along actin filaments pull the apicomplexan along the substrate. In this case, such movement is involved in actual host-cell penetration.
Microbial enterotypes beyond genus level: Bacteroides species as a predictive biomarker for weight change upon controlled intervention with arabinoxylan oligosaccharides in overweight subjects
Published in Gut Microbes, 2020
Lars Christensen, Claudia V. Sørensen, Frederikke U. Wøhlk, Louise Kjølbæk, Arne Astrup, Yolanda Sanz, Mads F. Hjorth, Alfonso Benítez-Páez
The functional assessment on the entire genomes using the Pfam annotation system permitted to assess the abundance of more than 3000 Pfam domains. The statistical test to determine the probable enrichment of such protein domains on B. cellulosilyticus genomes recovered 87 domain associations, and 54 of which had reliable functional annotations (Table 4). This analysis corroborated some previous observations during the CAZy gene survey. Thus, several domains associated with different GH and PL enzymes listed in Table 3, and related to xylan and glycosaminoglycan degradation were also retrieved (e.g., GH10, GH79, GH43, PL8) (Table 4). Moreover, we also observed that other domains linked to xylan binding and degradation were enriched in B. cellulosilyticus genomes (e.g., Glyco_hydro_30, CBM_6, Glyco_hydro_3, Bac_rhamnosid). Nevertheless, the glycan metabolism domains enriched in B. cellulosilyticus in comparison with other Bacteroides species is also accompanied by a higher abundance of polysaccharide degradation functions as well as of sensor and kinase subunits of several two-component systems specialized on carbohydrate uptake. Moreover, we detected an enrichment of some peptidase domains (Peptidase C25, Peptidase_M6 and Peptidase_C39), and domains of secreted proteins involved in adhesion (VCBS, fn3, Fn3-like), and flagella- and pili-independent gliding motility (SprA_N and PorP_SprF).
Novel drug targets for treatment of cryptosporidiosis
Published in Expert Opinion on Therapeutic Targets, 2020
Beilin Wang, Alejandro Castellanos-Gonzalez, A. Clinton White Jr
Protein kinases play essential roles in the biology of all eukaryotic cells, including protozoan parasites such as Cryptosporidium. Selective inhibitors of protein kinases have proven to be important targets for chemotherapy of malignancies [13,14]. Apicocomplexan parasites including Cryptosporidium, Toxoplasma, and Plasmodium all express calcium-dependent protein kinases (CDPK) homologous to mammalian enzymes. Apicomplexan CDPKs are important mediators of parasite gliding motility, invasion, and egress. However, the gatekeeper next to the catalytic site contains a glycine instead of bulkier residues found in mammalian CDPKs. Thus, parasite CDPKs are an important potential target for anti-Cryptosporidium drug development.
Correlates of malaria vaccine efficacy
Published in Expert Review of Vaccines, 2021
Danielle I. Stanisic, Matthew B. B. McCall
Sporozoite gliding motility is essential for traversal through the dermis and antibody-mediated inhibition is assessed by incubating serum with sporozoites and measuring the gliding trails of CSP [47]. The utility of this particular assay is somewhat limited as quantifying the trails is subjective [48] and it has demonstrated considerable intra- and inter-assay variability [47]. The capacity of antibodies to inhibit sporozoite traversal through human hepatocytes in vitro [47] can be evaluated in a flow cytometry-based assay that detects dextran incorporated by traversed, wounded cells. IgG induced by CPS immunization significantly inhibits sporozoite traversal; this inhibition was enhanced when complement was added into the assay [43].