scholarly journals Reductive Evolution in Bacteria:Buchnerasp.,Rickettsia prowazekiiandMycobacterium leprae

2001 ◽  
Vol 2 (1) ◽  
pp. 44-48 ◽  
Author(s):  
Jo Wixon
Keyword(s):  
Acyrthosiphon Pisum ◽  
Intracellular Bacteria ◽  
Human Pathogens ◽  
Orthologous Genes ◽  
Reductive Evolution ◽  
Obligate Intracellular ◽  
Growth Requirements ◽  
Obligate Intracellular Bacteria ◽  
The Relationship ◽  
Host Genes

Obligate intracellular bacteria commonly have much reduced genome sizes compared to their nearest free-living relatives. One reason for this is reductive evolution: the loss of genes rendered non-essential due to the intracellular habitat. This can occur because of the presence of orthologous genes in the host, combined with the ability of the bacteria to import the protein or metabolite products of the host genes. In this article we take a look at three such bacteria whose genomes have been fully sequenced.Buchnerais an endosymbiont of the pea aphid,Acyrthosiphon pisum, the relationship between these two organisms being so essential that neither can reproduce in the absence of the other.Rickettsia prowazekiiis the causative agent of louse-borne typhus in humans andMycobacterium lepraeinfection of humans leads to leprosy. Both of these human pathogens have fastidious growth requirements, which has made them very difficult to study.

scholarly journals The growing repertoire of genetic tools for dissecting chlamydial pathogenesis

2021 ◽  
Author(s):  
Arkaprabha Banerjee ◽  
David E Nelson
Keyword(s):  
Genetic Engineering ◽  
Intracellular Bacteria ◽  
Human Pathogens ◽  
Pathogenic Potential ◽  
Host Preferences ◽  
Genetic Tools ◽  
Obligate Intracellular ◽  
Obligate Intracellular Bacteria ◽  
Multiple Species

Abstract Multiple species of obligate intracellular bacteria in the genus Chlamydia are important veterinary and/or human pathogens. These pathogens all share similar biphasic developmental cycles and transition between intracellular vegetative reticulate bodies and infectious elementary forms, but vary substantially in their host preferences and pathogenic potential. A lack of tools for genetic engineering of these organisms has long been an impediment to the study of their biology and pathogenesis. However, the refinement of approaches developed in C. trachomatis over the last ten years, and adaptation of some of these approaches to other Chlamydia spp. in just the last few years, has opened exciting new possibilities for studying this ubiquitous group of important pathogens.

scholarly journals A SpoIID Homolog Cleaves Glycan Strands at the Chlamydial Division Septum

mBio ◽  
2019 ◽  
Vol 10 (4) ◽  
Author(s):  
Nicolas Jacquier ◽  
Akhilesh K. Yadav ◽  
Trestan Pillonel ◽  
Patrick H. Viollier ◽  
Felipe Cava ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Intracellular Bacteria ◽  
Human Pathogens ◽  
Content Type ◽  
Obligate Intracellular ◽  
Peptidoglycan Biosynthesis ◽  
Peptidoglycan Synthesis ◽  
Lytic Transglycosylase ◽  
Obligate Intracellular Bacteria

ABSTRACT Chlamydiales species are obligate intracellular bacteria lacking a classical peptidoglycan sacculus but relying on peptidoglycan synthesis for cytokinesis. While septal peptidoglycan biosynthesis seems to be regulated by MreB actin and its membrane anchor RodZ rather than FtsZ tubulin in Chlamydiales, the mechanism of peptidoglycan remodeling is poorly understood. An amidase conserved in Chlamydiales is able to cleave peptide stems in peptidoglycan, but it is not clear how peptidoglycan glycan strands are cleaved since no classical lytic transglycosylase is encoded in chlamydial genomes. However, a protein containing a SpoIID domain, known to possess transglycosylase activity in Bacillus subtilis, is conserved in Chlamydiales. We show here that the SpoIID homologue of the Chlamydia-related pathogen Waddlia chondrophila is a septal peptidoglycan-binding protein. Moreover, we demonstrate that SpoIID acts as a lytic transglycosylase on peptidoglycan and as a muramidase on denuded glycan strands in vitro. As SpoIID-like proteins are widespread in nonsporulating bacteria, SpoIID might commonly be a septal peptidoglycan remodeling protein in bacteria, including obligate intracellular pathogens, and thus might represent a promising drug target. IMPORTANCE Chlamydiales species are obligate intracellular bacteria and important human pathogens that have a minimal division machinery lacking the proteins that are essential for bacterial division in other species, such as FtsZ. Chlamydial division requires synthesis of peptidoglycan, which forms a ring at the division septum and is rapidly turned over. However, little is known of peptidoglycan degradation, because many peptidoglycan-degrading enzymes are not encoded by chlamydial genomes. Here we show that an homologue of SpoIID, a peptidoglycan-degrading enzyme involved in sporulation of bacteria such as Bacillus subtilis, is expressed in Chlamydiales, localizes at the division septum, and degrades peptidoglycan in vitro, indicating that SpoIID is not only involved in sporulation but also likely implicated in division of some bacteria.

scholarly journals New Frontiers in Type III Secretion Biology: the Chlamydia Perspective

2013 ◽  
Vol 82 (1) ◽  
pp. 2-9 ◽  
Author(s):  
K. E. Mueller ◽  
G. V. Plano ◽  
K. A. Fields
Keyword(s):  
Type Iii Secretion ◽  
Genetic Manipulation ◽  
Respiratory Pathogen ◽  
Intracellular Bacteria ◽  
Human Pathogens ◽  
Content Type ◽  
Obligate Intracellular ◽  
Type Iii ◽  
Obligate Intracellular Bacteria ◽  
Coding Capacity

ABSTRACTMembers of the orderChlamydialescomprise a group of exquisitely evolved parasites of eukaryotic hosts that extends from single-celled amoeba to mammals. The most notable are human pathogens and include the agent of oculogenital diseaseChlamydia trachomatis, the respiratory pathogenC. pneumoniae, and the zoonotic agentC. psittaci. All of these species are obligate intracellular bacteria that develop within parasitophorous vesicles termed inclusions. This demanding lifestyle necessitates orchestrated entry into nonphagocytic cells, creation of a privileged intracellular niche, and subversion of potent host defenses. All chlamydial genomes contain the coding capacity for a nonflagellar type III secretion system, and this mechanism has arisen as an essential contributor to chlamydial virulence. The emergence of tractable approaches to the genetic manipulation of chlamydiae raises the possibility of explosive progress in understanding this important contributor to chlamydial pathogenesis. This minireview considers challenges and recent advances that have revealed how chlamydiae have maintained conserved aspects of T3S while exploiting diversification to yield a system that exerts a fundamental role in the unique biology ofChlamydiaspecies.

scholarly journals Using Core Genome Alignments to Assign Bacterial Species

2018 ◽  
Author(s):  
Matthew Chung ◽  
James B. Munro ◽  
Julie C. Dunning Hotopp
Keyword(s):  
Dna Hybridization ◽  
Core Genome ◽  
Sequence Data ◽  
Bacterial Species ◽  
Intracellular Bacteria ◽  
Obligate Intracellular ◽  
Exponential Increase ◽  
Wide Range ◽  
Obligate Intracellular Bacteria ◽  
The Relationship

ABSTRACTWith the exponential increase in the number of bacterial taxa with genome sequence data, a new standardized method is needed to assign bacterial species designations using genomic data that is consistent with the classically-obtained taxonomy. This is particularly acute for unculturable obligate intracellular bacteria like those in the Rickettsiales, where classical methods like DNA-DNA hybridization cannot be used to define species. Within the Rickettsiales, species designations have been applied inconsistently, often obfuscating the relationship between organisms and the context for experimental results. In this study, we generated core genome alignments for a wide range of genera with classically defined species, includingArcobacter,Caulobacter,Erwinia,Neisseria,Polaribacter,Ralstonia,Thermus, as well as genera within the Rickettsiales includingRickettsia,Orientia,Ehrlichia,Neoehrlichia,Anaplasma,eorickettsia, andWolbachia. A core genome alignment sequence identity (CGASI) threshold of 96.8% was found to maximize the prediction of classically-defined species. Using the CGASI cutoff, theWolbachiagenus can be delineated into species that differ from the currently used supergroup designations, while theRickettsiagenus is delineated into nine species, as opposed to the current 27 species. Additionally, we find that core genome alignments cannot be constructed between genomes belonging to different genera, establishing a bacterial genus cutoff that suggests the need to create new genera from theAnaplasmaandNeorickettsia. By using core genome alignments to assign taxonomic designations, we aim to provide a high-resolution, robust method for bacterial nomenclature that is aligned with classically-obtained results.

scholarly journals Initial Characterization of the Two ClpP Paralogs ofChlamydia trachomatisSuggests Unique Functionality for Each

2018 ◽  
Vol 201 (2) ◽  
Author(s):  
Nicholas A. Wood ◽  
Krystal Y. Chung ◽  
Amanda M. Blocker ◽  
Nathalia Rodrigues de Almeida ◽  
Martin Conda-Sheridan ◽  
...  
Keyword(s):  
Host Cells ◽  
Developmental Cycle ◽  
Intracellular Bacteria ◽  
Clp Protease ◽  
Content Type ◽  
Sexually Transmitted ◽  
Obligate Intracellular ◽  
Developmental Form ◽  
Obligate Intracellular Bacteria

ABSTRACTMembers ofChlamydiaare obligate intracellular bacteria that differentiate between two distinct functional and morphological forms during their developmental cycle, elementary bodies (EBs) and reticulate bodies (RBs). EBs are nondividing small electron-dense forms that infect host cells. RBs are larger noninfectious replicative forms that develop within a membrane-bound vesicle, termed an inclusion. Given the unique properties of each developmental form of this bacterium, we hypothesized that the Clp protease system plays an integral role in proteomic turnover by degrading specific proteins from one developmental form or the other.Chlamydiaspp. have five uncharacterizedclpgenes,clpX,clpC, twoclpPparalogs, andclpB. In other bacteria, ClpC and ClpX are ATPases that unfold and feed proteins into the ClpP protease to be degraded, and ClpB is a deaggregase. Here, we focused on characterizing the ClpP paralogs. Transcriptional analyses and immunoblotting determined that these genes are expressed midcycle. Bioinformatic analyses of these proteins identified key residues important for activity. Overexpression of inactiveclpPmutants inChlamydiaspp. suggested independent function of each ClpP paralog. To further probe these differences, we determined interactions between the ClpP proteins using bacterial two-hybrid assays and native gel analysis of recombinant proteins. Homotypic interactions of the ClpP proteins, but not heterotypic interactions between the ClpP paralogs, were detected. Interestingly, protease activity of ClpP2, but not ClpP1, was detectedin vitro. This activity was stimulated by antibiotics known to activate ClpP, which also blocked chlamydial growth. Our data suggest the chlamydial ClpP paralogs likely serve distinct and critical roles in this important pathogen.IMPORTANCEChlamydia trachomatisis the leading cause of preventable infectious blindness and of bacterial sexually transmitted infections worldwide. Chlamydiae are developmentally regulated obligate intracellular pathogens that alternate between two functional and morphologic forms, with distinct repertoires of proteins. We hypothesize that protein degradation is a critical aspect to the developmental cycle. A key system involved in protein turnover in bacteria is the Clp protease system. Here, we characterized the two chlamydial ClpP paralogs by examining their expression inChlamydiaspp., their ability to oligomerize, and their proteolytic activity. This work will help understand the evolutionarily diverse Clp proteases in the context of intracellular organisms, which may aid in the study of other clinically relevant intracellular bacteria.

Infections caused by obligate intracellular bacteria

2017 ◽  
Author(s):  
Philippa C. Matthews
Keyword(s):  
Clinical Significance ◽  
Classification System ◽  
Q Fever ◽  
Intracellular Bacteria ◽  
Rickettsial Infection ◽  
Obligate Intracellular ◽  
Treatment And Prevention ◽  
Clinical Syndromes ◽  
Obligate Intracellular Bacteria ◽  
The Tropics

This chapter consists of short notes, diagrams, and tables to summarize infections caused by obligate intracellular bacteria. The chapter begins with a classification system to divide these organisms into Rickettsia, Anaplasma, Chlamydia, Coxiella, and Bartonella species. Separate sections then follow on the infections of most clinical significance for the tropics and subtropics, including the typhus group (caused by rickettsial infection) and Q fever. For ease of reference, each topic is broken down into sections, including classification, epidemiology, microbiology, pathophysiology, clinical syndromes, diagnosis, treatment, and prevention.

scholarly journals Vaccine Design and Vaccination Strategies against Rickettsiae

Vaccines ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 896
Author(s):  
Anke Osterloh
Keyword(s):  
Protective Immunity ◽  
Vaccine Development ◽  
Intracellular Bacteria ◽  
Obligate Intracellular ◽  
Vaccination Strategies ◽  
The Past ◽  
Rickettsial Infections ◽  
Causative Agents ◽  
Prophylactic Vaccines ◽  
Obligate Intracellular Bacteria

Rickettsioses are febrile, potentially lethal infectious diseases that are a serious health threat, especially in poor income countries. The causative agents are small obligate intracellular bacteria, rickettsiae. Rickettsial infections are emerging worldwide with increasing incidence and geographic distribution. Nonetheless, these infections are clearly underdiagnosed because methods of diagnosis are still limited and often not available. Another problem is that the bacteria respond to only a few antibiotics, so delayed or wrong antibiotic treatment often leads to a more severe outcome of the disease. In addition to that, the development of antibiotic resistance is a serious threat because alternative antibiotics are missing. For these reasons, prophylactic vaccines against rickettsiae are urgently needed. In the past years, knowledge about protective immunity against rickettsiae and immunogenic determinants has been increasing and provides a basis for vaccine development against these bacterial pathogens. This review provides an overview of experimental vaccination approaches against rickettsial infections and perspectives on vaccination strategies.

Rickettsioses

2020 ◽  
pp. 1230-1251
Author(s):  
Karolina Griffiths ◽  
Carole Eldin ◽  
Didier Raoult ◽  
Philippe Parola
Keyword(s):  
Scrub Typhus ◽  
Spotted Fever ◽  
Intracellular Bacteria ◽  
Spotted Fever Group ◽  
Orientia Tsutsugamushi ◽  
Obligate Intracellular ◽  
Metabolic Characteristics ◽  
The Past ◽  
Life Threatening ◽  
Obligate Intracellular Bacteria

Rickettsioses are mild to life-threatening zoonoses caused by obligate intracellular bacteria of the order Rickettsiales (family Rickettsiaceae). Arthropods, including ticks, fleas, and mites, are implicated as their vectors, reservoirs, or amplifiers. With an increasing number of new pathogens and recognition of new pathogenicity and affected geographical areas over the past few decades, there is a better understanding of the scope and importance of these pathogens, particularly as a paradigm to understanding emerging and remerging infections. The taxonomy has undergone numerous changes, with now three main groups classified as rickettsioses according to morphological, antigenic and metabolic characteristics: (1) Rickettsioses due to the bacteria of the genus Rickettsia, including the spotted fever group, typhus groups (Rickettsiaceae), (2) Ehrlichioses and Anaplasmoses due to bacteria of the Anaplasmataceae and (3) scrub typhus due to Orientia tsutsugamushi.

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