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Evolutionary Biology of Parasitism
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Levels of genetic variability are very high for outcrossing trichostrongyle parasites such as O. ostertagi mentioned previously. In contrast, consider the nematode Heterorhabditis marelatus, an obligate parasite of soil-dwelling insects. Box 7.2 describes the remarkable means employed by such nematodes to infect insects. One or a small number of juvenile nematodes colonizes any particular insect host. Furthermore, once mature, the nematodes reproduce hermaphroditically—reproduction is by selfing. Consequently, the amount of genetic variability among the progeny within any infrapopulation is low. Also, the amount of gene flow is limited as the infected insects do not move much and the nematodes themselves have limited dispersal ability. As a consequence, as compared to trichostrongyles from domestic ruminants, H. marelatus has much lower overall genetic diversity both within populations and across the species, a much more subdivided population structure and a low effective population size.
Antiviral Drugs as Tools for Nanomedicine
Published in Devarajan Thangadurai, Saher Islam, Charles Oluwaseun Adetunji, Viral and Antiviral Nanomaterials, 2022
Infectious agents such as viruses, bacteria, and parasites behave as etiological agents in ~20% of human cancers, out of which nearly 12% of cancers worldwide are caused by oncovirus, mostly seen in the developing world (de Martel et al. 2017) (Figure 12.5). Viruses are very small particles nearly in size range of 20–30 nm, obligate parasite with either ds- or ss-DNA or RNA enclosed within a protein shell called capsid. Understanding and managing such cancers is facing daunting challenges due to unavailability of suitable animal models for pre-clinical studies to evaluate the potential immuno-prophylactic therapies. Another difficulty lies with the contrasting nature of viruses, their distinct types, and their interaction with host cell.
Application of Next-Generation Plant-Derived Nanobiofabricated Drugs for the Management of Tuberculosis
Published in Richard L. K. Glover, Daniel Nyanganyura, Rofhiwa Bridget Mulaudzi, Maluta Steven Mufamadi, Green Synthesis in Nanomedicine and Human Health, 2021
Charles Oluwaseun Adetunji, Olugbenga Samuel Michael, Muhammad Akram, Kadiri Oseni, Ajayi Kolawole Temidayo, Osikemekha Anthony Anani, Akinola Samson Olayinka, Olerimi Samson E, Wilson Nwankwo, Iram Ghaffar, Juliana Bunmi Adetunji
Mycobacterium tuberculosis (Mtb) is a non-motile, non-sporulating, strict aerobe, acid-fast rod that usually shows up unstained with Gram stain but, like all mycobacteria, appears stained with arylmethane dyes such as carbolfuchsin and rhodamine. It is viewed as curved bacilli microscopically with size as 1–4 µm in length and 0.3–0.6 µm in width (Sakamoto, 2012; Dunn et al., 2016). Alongside other bacteria like Corynebacterium, Nocardia and Rhodococcus, the genus Mycobacterium falls under the order Actinomycetales. As intracellular pathogenic bacteria, Mtb replicate within macrophages and monocytes, which are phagocytic cells. Many species of mycobacteria are environmental, but Mtb is an obligate parasite. In culture media, Mtb is a slow-growing species with a 12- to 24-hour cell division rate and long culture period of about 21 days on agar (Sakamoto, 2012).
Isolation and cultivation of candidate phyla radiation Saccharibacteria (TM7) bacteria in coculture with bacterial hosts
Published in Journal of Oral Microbiology, 2020
Pallavi P. Murugkar, Andrew J. Collins, Tsute Chen, Floyd E. Dewhirst
The first roadblock was the assumption that Saccharibacteria were simply fastidious bacteria that were capable of axenic growth in a complex medium under the proper culture conditions. We now know that all Saccharibacteria isolated to date are obligate parasites that require the presence of live bacterial hosts. Thus, anyone using Koch’s approach of streaking for isolation and axenic culture was doomed to fail because it excludes the necessary bacterial host. The idea that obligate parasitic organisms require a host is an old concept in biology, but possibly under-appreciated by the microbiologists attempting to culture candidate phyla bacteria before the isolation of TM7x. It is well recognized that there are bacterial parasites of eukaryotic cells such as members of the genera Chlamydia and Mycoplasma, the insect endosymbiont Buchnera spp [51], and Vampirovibrio chlorellavorus, a small, 0.6-micron diameter, epi-parasite of the green alga Chorella vulgaris [52]. However, awareness of the fact that bacteria parasitize other bacteria was generally overlooked except for Bdellovibrio bacteriovorus and related bacteria [53]. Therefore, despite solid literature on specific prokaryotes being parasites on other prokaryotes, there are no reports that microbiologists attempted to culture CPR bacteria in binary coculture before the isolation of TM7x. It appears that most investigators attempted to obtain pure cultures directly following Koch’s approach.
Endophthalmitis following Suture Removal – Clinical Outcomes and Microbiological Profile
Published in Seminars in Ophthalmology, 2019
Bhavik Panchal, Mudit Tyagi, Avinash Pathengay, Savitri Sharma, Vivek P Dave, Uppal Gandhi, Divya Balakrishnan, Rajeev R. Pappuru, Joveeta Joseph, Ramesha Kekunnaya, Taraprasad Das
The organisms isolated in the study included Streptococcus pneumoniae (7/11), Hemophilus influenzae (1/11) and Achromobacter denitrificans (1/11). S. pneumoniae is a Gram-positive aerobic bacteria. It is an obligate parasite in the human body, and it is found in the nasopharynx of healthy people. Apart from the nose and nasopharynx, it is also isolated from the eye and the ear. In most people, the colonization is asymptomatic and does not cause the disease.10,11 Colonization is more common in children than in adults.12 The highest rate of representation of S. pneumoniae was observed in children aged up to 6 years.13 In our series, all cases infected by S. pneumonia belong to the pediatric age group. Studies have shown that endophthalmitis secondary to S. pneumoniae is associated with poor outcomes.14 All the above cases in our series had a poor outcome. Similarly, H. influenzae is a gram-negative, coccobacillus found in the nasopharynx and may lead to infection in a similar way to S. pneumonia.14
Discovery of novel drugs for Chagas disease: is carbonic anhydrase a target for antiprotozoal drugs?
Published in Expert Opinion on Drug Discovery, 2022
Alane Beatriz Vermelho, Giseli Capaci Rodrigues, Alessio Nocentini, Felipe R. P. Mansoldo, Claudiu T. Supuran
The protozoan Plasmodium falciparum is an obligate parasite and the causative agent of human malaria [25,37]. Del Prete et al. demonstrated that the CA of Plasmodium falciparum (PfCA), which was previously assigned to the α‐CA class, actually belongs to an undisclosed family of CAs named η-CA. The authors detected several characteristics of PfCA that are not typical of an α‐class enzyme, which can be briefly highlighted: (i) the predicted metal ion coordinating residues are His299, His301, and Gln320; (2) the proton shuttle residue of an α‐is unknown as they do not have His in position 64 (considering the numbering of the human enzymes); (iii) the gate-keeping residues Glu106 – Thr199 which is present in all α-CAs are absent in η-class enzymes; (iv) the η-CAs have a much longer amino acid sequence compared to α-CAs, which typically incorporate 250–280 amino acid residues. The PfCA CO2 hydrase activity was measured by a stopped-flow assay method, showing an excellent catalytic activity at pH 7.5, with a kcat of 1.4 × 105 s−1 and a kcat/km of 5.4 × 106 M−1 s−1 [37]. Although α-, γ-, and β-CAs are common in eukaryotic and prokaryotic organisms, the distribution of η-CAs is limited, having been identified only in species of Plasmodium. All CAs known to date contain the metal cofactor (mostly Zn2+, rarely Cd2+, Co2+, Fe2+, and Mn2+) [38]. Regarding the use of ions in the active site to perform catalysis reaction: α-, β-, δ-, η-CAs use Zn2+ ions and ζ-class uses Cd2+ [39]. The metal ions are coordinated in the active site by amino acids that are arranged in a distinct motif for each CA class: three histidines for α-, γ-, δ-class CAs; one histidine and two cysteines for β- and ζ-class CAs [40]; and two histidine and one glutamine in the η-class [41]. There is no information available on the structure of η-CAs and the role of η-CAs class is poorly understood, but they may be involved in de novo purine/pyrimidine biosynthetic pathways [24]. Although no esterase activity was reported for other CA families, some studies report the hydrolysis of esters/thioesters by α-, η-, θ- and ι-CAs [42]. Krungkrai’s group reported that PfaCA has esterase activity with inhibition with primary sulphonamides [43], later Supuran’s group showed that coumarins act as PfaCA inhibitors and highlighted that the effectively inhibition of this enzyme is only possible due to the esterase activity of PfaCA [44].