scholarly journals Characterisation of the phase-variable autotransporter Lav reveals a role in host cell adherence and biofilm formation in Non-Typeable Haemophilus influenzae

2021 ◽  
Author(s):  
Zachary N. Phillips ◽  
Preeti Garai ◽  
Greg Tram ◽  
Asma-Ul Husna ◽  
Megan Staples ◽  
...  
Keyword(s):  
Haemophilus Influenzae ◽  
Biofilm Formation ◽  
Host Cells ◽  
Phase Variable ◽  
Passenger Domain ◽  
Neisseria Species ◽  
Distinct Lineage ◽  
Expression Status ◽  
Lineage Distribution

Lav is an autotransporter protein found in pathogenic Haemophilus and Neisseria species. Lav in non-typeable Haemophilus influenzae (NTHi) is phase-variable: the gene reversibly switches ON-OFF via changes in length of a locus-located GCAA(n) simple DNA sequence repeat tract. The expression status of lav was examined in carriage and invasive collections of NTHi, where it was predominantly not expressed (OFF). Phenotypic study showed lav expression (ON) results in increased adherence to host cells, and denser biofilm formation. A survey of Haemophilus spp. genome sequences showed lav is present in ~60% of NTHi strains, but lav is not present in most typeable H. influenzae. Sequence analysis revealed a total of five distinct variants of the Lav passenger domain present in Haemophilus spp., with these five variants showing a distinct lineage distribution. Determining the role of Lav in NTHi will help understand the role of this protein during distinct pathologies.

scholarly journals The role of Dam methylation in phase variation of Haemophilus influenzae genes involved in defence against phage infection

Microbiology ◽  
2005 ◽  
Vol 151 (10) ◽  
pp. 3361-3369 ◽  
Author(s):  
Piotr Zaleski ◽  
Marek Wojciechowski ◽  
Andrzej Piekarowicz
Keyword(s):  
Haemophilus Influenzae ◽  
Phase Variation ◽  
Phage Infection ◽  
Phase Variable ◽  
Repeat Tract ◽  
Insertional Inactivation ◽  
Phage Dna ◽  
Dam Methylation ◽  
Tetranucleotide Repeats

Haemophilus influenzae uses phase variation (PV) to modulate the activity of its defence systems against phage infection. The PV of the restriction–modification (R-M) system HindI, the main defence system against phage infection and incoming chromosomal and phage DNA in H. influenzae Rd, is driven by changes of the pentanucleotide repeat tract within the coding sequence of the hsdM gene and is influenced by lack of Dam methylation. Phase-variable resistance/sensitivity to phage infection correlates with changes in lipooligosaccharide (LOS) structure and occurs by slippage of tetranucleotide repeats within the gene lic2A, coding for a step in the biosynthesis of LOS. The lack of Dam activity destabilizes the tetranuclotide (5′-CAAT) repeat tract and increases the frequency of switching from sensitivity to resistance to phage infection more than in the opposite direction. The PV of the lgtC gene does not influence resistance or sensitivity to phage infection. Insertional inactivation of lic2A, but not lgtC or lgtF, leads to resistance to phage infection and to the same structure of the LOS as observed among phase-variable phage-resistant variants. This indicates that in the H. influenzae Rd LOS only the first two sugars (Glc-Gal) extending from the third heptose are part of bacterial phage receptors.

scholarly journals Epigenetic Regulation Alters Biofilm Architecture and Composition in Multiple Clinical Isolates of Nontypeable Haemophilus influenzae

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Kenneth L. Brockman ◽  
Patrick N. Azzari ◽  
M. Taylor Branstool ◽  
John M. Atack ◽  
Benjamin L. Schulz ◽  
...  
Keyword(s):  
Respiratory Tract ◽  
Haemophilus Influenzae ◽  
Otitis Media ◽  
Biofilm Formation ◽  
Human Pathogens ◽  
Content Type ◽  
Alkaline Conditions ◽  
Tract Infections ◽  
Biofilm Structure

ABSTRACT Biofilms play a critical role in the colonization, persistence, and pathogenesis of many human pathogens. Multiple mucosa-associated pathogens have evolved a mechanism of rapid adaptation, termed the phasevarion, which facilitates a coordinated regulation of numerous genes throughout the bacterial genome. This epigenetic regulation occurs via phase variation of a DNA methyltransferase, Mod. The phasevarion of nontypeable Haemophilus influenzae (NTHI) significantly affects the severity of experimental otitis media and regulates several disease-related processes. However, the role of the NTHI phasevarion in biofilm formation is unclear. The present study shows that the phasevarions of multiple NTHI clinical isolates regulate in vitro biofilm formation under disease-specific microenvironmental conditions. The impact of phasevarion regulation was greatest under alkaline conditions that mimic those known to occur in the middle ear during disease. Under alkaline conditions, NTHI strains that express the ModA2 methyltransferase formed biofilms with significantly greater biomass and less distinct architecture than those formed by a ModA2-deficient population. The biofilms formed by NTHI strains that express ModA2 also contained less extracellular DNA (eDNA) and significantly less extracellular HU, a DNABII DNA-binding protein critical for biofilm structural stability. Stable biofilm structure is critical for bacterial pathogenesis and persistence in multiple experimental models of disease. These results identify a role for the phasevarion in regulation of biofilm formation, a process integral to the chronic nature of many infections. Understanding the role of the phasevarion in biofilm formation is critical to the development of prevention and treatment strategies for these chronic diseases. IMPORTANCE Upper respiratory tract infections are the number one reason for a child to visit the emergency department, and otitis media (middle ear infection) ranks third overall. Biofilms contribute significantly to the chronic nature of bacterial respiratory tract infections, including otitis media, and make these diseases particularly difficult to treat. Several mucosa-associated human pathogens utilize a mechanism of rapid adaptation termed the phasevarion, or phase variable regulon, to resist environmental and host immune pressures. In this study, we assessed the role of the phasevarion in regulation of biofilm formation by nontypeable Haemophilus influenzae (NTHI), which causes numerous respiratory tract diseases. We found that the NTHI phasevarion regulates biofilm structure and critical biofilm matrix components under disease-specific conditions. The findings of this work could be significant in the design of improved strategies against NTHI infections, as well as diseases due to other pathogens that utilize a phasevarion.

scholarly journals Co-Circulation of Chikungunya and Multiple DENV Serotypes and Genotypes, Western Indonesia 2015–2016

Viruses ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 99
Author(s):  
Harapan Harapan ◽  
Alice Michie ◽  
Timo Ernst ◽  
Kritu Panta ◽  
Mudatsir Mudatsir ◽  
...  
Keyword(s):  
Epidemiological Surveillance ◽  
Health Concern ◽  
Genotype I ◽  
Denv Serotypes ◽  
Indonesian Archipelago ◽  
Study Results ◽  
Distinct Lineage ◽  
One Year ◽  
Lineage Distribution

Dengue is a mosquito-borne disease of public health concern affecting tropical and subtropical countries, including Indonesia. Although studies on dengue epidemiology have been undertaken in Indonesia, data are lacking in many areas of the country. The aim of this study was to determine dengue virus (DENV) and chikungunya virus (CHIKV) molecular epidemiology in western regions of the Indonesian archipelago. A one-year prospective study was conducted in Aceh and Jambi in 2015 and 2016, respectively, where patients with dengue-like illness were enrolled. Of 205 patients recruited, 29 and 27 were confirmed with dengue in Aceh and Jambi, respectively, and three from Jambi were confirmed with chikungunya. DENV-1 was the predominant serotype identified in Aceh while DENV-2 was predominant in Jambi. All DENV-1 and DENV-2 from both regions were classified as Genotype I and Cosmopolitan genotype, respectively, and all DENV-3 viruses from Jambi were Genotype I. Some viruses, in particular DENV-1, displayed a distinct lineage distribution, where two DENV-1 lineages from Aceh were more closely related to viruses from China instead of Jambi highlighting the role of travel and flight patterns on DENV transmission in the region. DENV-2 from both Aceh and Jambi and DENV-3 from Jambi were all closely related to Indonesian local strains. All three CHIKV belonged to Asian genotype and clustered closely with Indonesian CHIKV strains including those previously circulating in Jambi in 2015, confirming continuous and sustainable transmission of CHIKV in the region. The study results emphasize the importance of continuous epidemiological surveillance of arboviruses in Indonesia and simultaneous testing for CHIKV among dengue-suspected patients.

scholarly journals Role of Porphyromonas gingivalis’s peptidylarginine deiminase in multispecies biofilm formation and bacterial adherence to host cells

2017 ◽  
Vol 9 (sup1) ◽  
pp. 1325247
Author(s):  
Ardita Aliko ◽  
Marta Kamińska ◽  
Brith Bergum ◽  
Annelie Hellvard ◽  
Roland Jonsson ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Bacterial Adherence ◽  
Host Cells ◽  
Peptidylarginine Deiminase ◽  
Multispecies Biofilm

scholarly journals Role of biofilm formation in the persistent colonization of Haemophilus influenzae in children from northern India

2009 ◽  
Vol 58 (11) ◽  
pp. 1428-1432 ◽  
Author(s):  
Sasanka Sekhar ◽  
Rajesh Kumar ◽  
Anuradha Chakraborti
Keyword(s):  
Haemophilus Influenzae ◽  
Biofilm Formation ◽  
Population Based ◽  
Population Based Study ◽  
True Nature ◽  
Northern India ◽  
Need To Evaluate ◽  
Clonal Distribution ◽  
Long Time

The human nasopharynx is a major ecological niche for Haemophilus influenzae colonization. Establishment of infection is critically dependent on the persistence of bacteria in the nasopharynx. Various factors are presumed to mediate this persistence and the influence of biofilm formation has been under scrutiny for a long time. In a prospective population-based study, the nasopharyngeal colonization pattern of 250 children <2 years old was traced to gain further insights into the phenomenon. The association between biofilm formation and persistence was delineated by quantitative biofilm assay, while the true nature of biofilm formers was further evaluated by electron microscopy studies. H. influenzae isolates obtained in this study, when analysed by phenotypic and genotypic means, revealed a clonal distribution of strains within the population. The biofilm formation ability of the isolates was found to be significantly associated with bacterial persistence (P<0.001). The isolates having biofilm formation ability were found to be 7.1 times more likely to persist in the nasopharynx than non-biofilm formers. This study provides direct evidence indicating the intricate relationship between biofilm formation and the persistence of bacteria. Our results emphasize the need to evaluate the potential for biofilm formation before designing preventive and therapeutic strategies.

scholarly journals Edwardsiella piscicida YefM-YoeB: A Type II Toxin-Antitoxin System That Is Related to Antibiotic Resistance, Biofilm Formation, Serum Survival, and Host Infection

2021 ◽  
Vol 12 ◽  
Author(s):  
Dongmei Ma ◽  
Hanjie Gu ◽  
Yanjie Shi ◽  
Huiqin Huang ◽  
Dongmei Sun ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Pathogenic Bacteria ◽  
Wild Strain ◽  
Host Cells ◽  
Resistant Bacteria ◽  
Serum Resistance ◽  
Type Ii ◽  
Edwardsiella Piscicida

The emergence of drug resistant bacteria is a tricky and confronted problem in modern medicine, and one of important reasons is the widespread of toxin-antitoxin (TA) systems in pathogenic bacteria. Edwardsiella piscicida (also known as E. tarda) is the leading pathogen threatening worldwide fresh and seawater aquaculture industries and has been considered as a model organism for studying intracellular and systemic infections. However, the role of type II TA systems are completely unknown in aquatic pathogenic bacteria. In this study, we identified and characterized a type II TA system, YefM-YoeB, of E. piscicida, where YefM is the antitoxin and YoeB is the toxin. yefM and yoeB are co-expressed in a bicistronic operon. When expressed in E. coli, YoeB cause bacterial growth arrest, which was restored by the addition of YefM. To investigate the biological role of the TA system, two markerless yoeB and yefM-yoeB in-frame mutant strains, TX01ΔyoeB and TX01ΔyefM-yoeB, were constructed, respectively. Compared to the wild strain TX01, TX01ΔyefM-yoeB exhibited markedly reduced resistance against oxidative stress and antibiotic, and markedly reduced ability to form persistent bacteria. The deletion of yefM-yoeB enhanced the bacterial ability of high temperature tolerance, biofilm formation, and host serum resistance, which is the first study about the relationship between type II TA system and serum resistance. In vitro infection experiment showed that the inactivation of yefM-yoeB greatly enhanced bacterial capability of adhesion in host cells. Consistently, in vivo experiment suggested that the yefM-yoeB mutation had an obvious positive effect on bacteria dissemination of fish tissues and general virulence. Introduction of a trans-expressed yefM-yoeB restored the virulence of TX01ΔyefM-yoeB. These findings suggest that YefM-YoeB is involved in responding adverse circumstance and pathogenicity of E. piscicida. In addition, we found that YefM-YoeB negatively autoregulated the expression of yefM-yoeB and YefM could directly bind with own promoter. This study provides first insights into the biological activity of type II TA system YefM-YoeB in aquatic pathogenic bacteria and contributes to understand the pathogenesis of E. piscicida.

scholarly journals Role of Lipopolysaccharide Phase Variation in Susceptibility of Haemophilus influenzae to Bactericidal Immunoglobulin M Antibodies in Rabbit Sera

2000 ◽  
Vol 68 (5) ◽  
pp. 2804-2807 ◽  
Author(s):  
Alice L. Erwin ◽  
Yambasu A. Brewah ◽  
Debra A. Couchenour ◽  
Philip R. Barren ◽  
Stephen J. Burke ◽  
...  
Keyword(s):  
Haemophilus Influenzae ◽  
Human Serum ◽  
Clinical Isolate ◽  
Bactericidal Activity ◽  
Phase Variation ◽  
Immunoglobulin M ◽  
Second Phase ◽  
Phase Variable ◽  
Igm Antibodies

ABSTRACT The effect of phase variation of lipopolysaccharide (LPS) structure on the susceptibility of Haemophilus influenzae to complement-dependent killing by normal human sera and normal rat sera has been described previously. The phase-variable structure phosphorylcholine (ChoP) confers susceptibility to human serum, since ChoP on the bacterial cell surface binds to serum C-reactive protein and activates complement. In contrast, expression of galα1,4gal, a second phase-variable epitope that is also found on human glycoconjugates, confers resistance to human serum. We studied the role of phase variation of these structures in the susceptibilities ofH. influenzae KW20 (Rd) and a clinical isolate of nontypeable H. influenzae to killing by rabbit sera, which often possess naturally acquired complement-dependent bactericidal activity for unencapsulated H. influenzae. Expression of ChoP increased the resistance of strain KW20 to killing by bactericidal rabbit sera. In contrast, the serum resistance of a clinical isolate, H233, was unaffected by ChoP expression but was reduced by galα1,4gal expression. The rabbit sera with bactericidal activity (but not the nonbactericidal sera) all contained immunoglobulin M (IgM) antibodies able to bind to the surface of H. influenzae bacteria, as detected by flow cytometry, and contained IgM antibodies to LPS purified from strain KW20. Preincubation of sera with LPS reduced their bactericidal activity. Bactericidal activity was recovered quantitatively in an IgM-enriched fraction of sera. It is concluded that naturally occuring bactericidal activity for unencapsulatedH. influenzae is largely due to IgM antibodies directed against phase-variable structures of the LPS.

scholarly journals Altered proteome of a Burkholderia pseudomallei mutant defective in short-chain dehydrogenase affects cell adhesion, biofilm formation and heat stress tolerance

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8659 ◽  
Author(s):  
Onrapak Reamtong ◽  
Nitaya Indrawattana ◽  
Amporn Rungruengkitkun ◽  
Tipparat Thiangtrongjit ◽  
Taksaon Duangurai ◽  
...  
Keyword(s):  
Heat Stress ◽  
Biofilm Formation ◽  
Burkholderia Pseudomallei ◽  
Deletion Mutant ◽  
Stress Conditions ◽  
Host Cells ◽  
Short Chain ◽  
Wild Type ◽  
Short Chain Dehydrogenase

Burkholderia pseudomallei is a Gram-negative bacillus that causes melioidosis and is recognized as an important public health problem in southeast Asia and northeast Australia. The treatment of B. pseudomallei infection is hampered by resistance to a wide range of antimicrobial agents and no vaccine is currently available. At present, the underlying mechanisms of B. pseudomallei pathogenesis are poorly understood. In our previous study, we reported that a B. pseudomallei short-chain dehydrogenase (SDO; BPSS2242) mutant constructed by deletion mutagenesis showed reduced B. pseudomallei invasion and initial intracellular survival. This indicated that SDO is associated with the pathogenesis of melioidosis. In the present study, the role of B. pseudomallei SDO was further investigated using the SDO deletion mutant by a proteomic approach. The protein profiles of the SDO mutant and wild-type K96243 were investigated through gel-based proteomic analysis. Quantitative intensity analysis of three individual cultures of the B. pseudomallei SDO mutant revealed significant down-regulation of five protein spots compared with the wild-type. Q-TOF MS/MS identified the protein spots as a glutamate/aspartate ABC transporter, prolyl-tRNA synthetase, Hsp70 family protein, quinone oxidoreductase and a putative carboxypeptidase. Functional assays were performed to investigate the role of these differentially expressed proteins in adhesion to host cells, biofilm induction and survival under heat stress conditions. The SDO deletion mutant showed a decreased ability to adhere to host cells. Moreover, biofilm formation and the survival rate of bacteria under heat stress conditions were also reduced in the mutant strain. Our findings provide insight into the role of SDO in the survival and pathogenesis of B. pseudomallei at the molecular level, which may be applied to the prevention and control of B. pseudomallei infection.

scholarly journals Phase variable glycosylation in non-typeable Haemophilus influenzae

2019 ◽  
Author(s):  
Danila Elango ◽  
Benjamin L. Schulz
Keyword(s):  
Haemophilus Influenzae ◽  
Ex Vivo ◽  
Phase Variation ◽  
Population Diversity ◽  
Site Directed Mutagenesis ◽  
Host Cells ◽  
Phase Variable ◽  
Repeat Elements ◽  
C Terminus ◽  
Tract Infections

AbstractNon-typeable Haemophilus influenzae (NTHi) is a leading cause of respiratory tract infections worldwide and continues to be a global health burden. Adhesion and colonisation of host cells are crucial steps in bacterial pathogenesis, and in many strains of NTHi interaction with the host is mediated by the high molecular weight adhesins HMW1A and HMW2A. These adhesins are N-glycoproteins which are modified by cytoplasmic glycosyltransferases HMW1C and HMW2C. Phase variation in the number of short sequence repeats in the promoters of hmw1A and hmw2A directly affects their expression. Here, we report the presence of similar variable repeat elements in the promoters of hmw1C and hmw2C in diverse NTHi isolates. In an ex vivo assay, we systematically altered substrate and glycosyltransferase expression and showed that both of these factors affected the site-specific efficiency of glycosylation on HMW-A. Glycosylation occupancy was incomplete at many sites, variable between sites, and generally lower close to the C-terminus of HMW-A. We investigated the causes of this variability. As HMW-C glycosylates HMW-A in the cytoplasm, we tested how secretion affected glycosylation on HMW-A and showed that retaining HMW-A in the cytoplasm indeed increased glycosylation occupancy across the full length of the protein. Site-directed mutagenesis showed that HMW-C had no inherent preference for glycosylating asparagines in NxS or NxT sequons. This work provides key insights into factors contributing to the heterogenous modifications of NTHi HMW-A adhesins, expands knowledge of NTHi population diversity and pathogenic capability, and is relevant to vaccine design for NTHi and related pathogens.

The role of lex2 in lipopolysaccharide biosynthesis in Haemophilus influenzae strains RM7004 and RM153

Microbiology ◽  
2003 ◽  
Vol 149 (11) ◽  
pp. 3165-3175 ◽  
Author(s):  
Ruth Griffin ◽  
Andrew D. Cox ◽  
Katherine Makepeace ◽  
James C. Richards ◽  
E. Richard Moxon ◽  
...  
Keyword(s):  
Haemophilus Influenzae ◽  
Inner Core ◽  
Phase Variable ◽  
Specific Monoclonal Antibody ◽  
Variable Expression ◽  
Sequence Identity ◽  
Lipopolysaccharide Biosynthesis ◽  
Serotype B ◽  
Reading Frames

The locus lex2, comprising lex2A and lex2B, contributes to the phase-variable expression of lipopolysaccharide (LPS) of Haemophilus influenzae and was found to be present in 74 % of strains investigated. lex2A contains 5′-GCAA repeats which vary in number from 4 to 46 copies between strains. The locus was cloned from the serotype b strains RM7004 and RM153 and showed >99 % nucleotide sequence identity between these strains and the published lex2 sequence. Disruption of the lex2B gene in strain RM7004 resulted in truncation of some LPS glycoforms, shown by gel fractionation, with only one glycoform reacting with a digalactoside-specific monoclonal antibody, 4C4, compared with four LPS glycoforms in the more elongated LPS of the parent strain. Mass spectrometry and NMR analyses of LPS from the lex2B mutant revealed loss of the terminal digalactoside as well as the second β-glucose extending from the first heptose of the inner core. The authors conclude that Lex2B is the β-(1-4)-glucosyltransferase that adds the second β-glucose to the first β-glucose as part of the oligosaccharide extension from the first heptose of the LPS of strain RM7004. Investigation of the expression of the lex2 locus indicated that the genes are co-transcribed and that both reading frames are required for addition of this second β-glucose in a phase-variable manner.

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