scholarly journals Effect of Melanin and Carotenoids ofExophiala (Wangiella) dermatitidis on Phagocytosis, Oxidative Burst, and Killing by Human Neutrophils

1999 ◽  
Vol 67 (1) ◽  
pp. 94-101 ◽  
Author(s):  
Norbert Schnitzler ◽  
Heidrun Peltroche-Llacsahuanga ◽  
Nicole Bestier ◽  
Josef Zündorf ◽  
Rudolf Lütticken ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Oxidative Burst ◽  
Fungal Pathogen ◽  
Type Strain ◽  
Wild Type Strain ◽  
Redox Properties ◽  
Colony Count ◽  
Human Neutrophils ◽  
Wild Type ◽  
Neutrophil Oxidative Burst

ABSTRACT The black yeast Exophiala (Wangiella)dermatitidis is an increasingly recognized pathogen and a leading cause of severe pheohyphomycosis. Melanin is thought to contribute to the virulence of E. dermatitidis. Whereas the synthesis and the redox properties of melanin have been studied intensively, the influence of melanin and carotenoids on the phagocytosis, the oxidative burst, and the killing of E. dermatitidis by human neutrophils has not been studied. To study their effects on these phenomena, we applied a combination of flow cytometry and a colony-count-dependent method. Using E. dermatitidis wild-type strain 8565 and several melanin-deficient mutants that have been described previously, we demonstrate that melanin prevents this pathogen from being killed in the phagolysosome of the neutrophils. Melanin did not influence the phagocytosis or the oxidative burst of the neutrophils involved. The carotenoids torulene and torularhodine were not found to contribute to the prevention of killing. The ability of E. dermatitidis to block the effects of the neutrophil oxidative burst may critically impair the potential of the host to sufficiently eliminate this fungal pathogen and thus may play an important role in the pathogenesis of phaeohyphomycosis.

Impact of sarA Mutation on Immune System Evasion and Stress Response in Staphylococcus aureus

2020 ◽  
Vol 29 (3) ◽  
pp. 105-112
Author(s):  
Yomna A. Hagag ◽  
Abdelaziz Elgaml ◽  
Ramadan Hassan ◽  
Hany I. Kenawy
Keyword(s):  
Staphylococcus Aureus ◽  
Immune System ◽  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Human Neutrophils ◽  
Bacterial Survival ◽  
Wild Type ◽  
The Impact

Background: Staphylococcus aureus is a major human pathogen responsible for a large number of infections. In S. aureus, SarA is an important global locus responsible for the regulation of virulence factors, as well as biofilm formation. Objectives: The aim of this work is to clarify the impact of SarA on biofilm formation, immune system evasion, as well as the survival of S. aureus under stress conditions. Methodology: A comparative study between S. aureus wild type strain, sarA mutant and complemented strains was established addressing the biofilm formation, opsonization, phagocytosis, as well as ability of the bacterium to survive in stressful environments including acidic pH, hyperosmotic and oxidative stress. The in vitro experiments were confirmed by challenging of mice via intraperitoneal injection with the wild type strain, sarA mutant and complemented strains. Results: Mutation of sarA diminished significantly biofilm formation. Moreover, this mutation resulted in a slight decrease in the deposition of the most important opsonin in complement-mediated immunity, named C3 on S. aureus cells. However, this mutation was associated with a significant enhancement of bacterial phagocytosis and killing by human neutrophils. Furthermore, this mutation altered bacterial survival in stressful conditions. It is also noteworthy that sarA mutation resulted in a significant higher survival rates during the challenging of mice. Conclusion: SarA plays a role as a key regulator of biofilm formation, which in turn has a great impact on immune system evasion through affecting opsonization and phagocytosis. In addition, SarA improves the ability of S. aureus to survive in stressful conditions.

scholarly journals Neutralizing Antibodies to Adenylate Cyclase Toxin Promote Phagocytosis of Bordetella pertussis by Human Neutrophils

2000 ◽  
Vol 68 (12) ◽  
pp. 7152-7155 ◽  
Author(s):  
Christine L. Weingart ◽  
Paula S. Mobberley-Schuman ◽  
Erik L. Hewlett ◽  
Mary C. Gray ◽  
Alison A. Weiss
Keyword(s):  
Monoclonal Antibodies ◽  
Adenylate Cyclase ◽  
Bordetella Pertussis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Immune Serum ◽  
Human Neutrophils ◽  
Wild Type ◽  
Human Immune ◽  
Adenylate Cyclase Toxin

ABSTRACT A previous study showed that opsonization with human immune serum could either promote or antagonize phagocytosis of Bordetella pertussis by human neutrophils depending on whether the bacteria expressed adenylate cyclase toxin. Opsonization of the wild-type strain inhibited phagocytosis relative to unopsonized controls. In contrast, mutants lacking adenylate cyclase toxin were efficiently phagocytosed when opsonized with human immune serum. In this study, we examined opsonization in the presence or absence of monoclonal antibodies to adenylate cyclase toxin. Addition of neutralizing monoclonal antibodies to adenylate cyclase toxin converted a serum that previously inhibited both attachment and phagocytosis of the wild-type strain to one that increased both attachment and phagocytosis compared to the no-serum control. Monoclonal antibodies that recognize the adenylate cyclase toxin but fail to neutralize activity were without effect. These results suggest that adenylate cyclase toxin inhibits both Fc receptor-mediated attachment and phagocytosis of B. pertussis by neutrophils.

A compensatory increase in trehalose synthesis in response to desiccation stress in Saccharomyces cerevisiae cells lacking the heat shock protein Hsp12p

2008 ◽  
Vol 54 (7) ◽  
pp. 559-568 ◽  
Author(s):  
Vanessa J. Shamrock ◽  
George G. Lindsey
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Flow Cytometry ◽  
Type Strain ◽  
Wild Type Strain ◽  
Membrane Integrity ◽  
Oxygen Species ◽  
Wild Type ◽  
Plasma Membrane Integrity ◽  
Trehalose Synthesis

The effect of HSP12 deletion on the response of yeast to desiccation was investigated. The Δhsp12 strain was found to be more desiccation tolerant than the wild-type strain. Furthermore, the increased intracellular trehalose levels in the Δhsp12 strain suggested that this strain compensated for the lack of Hsp12p synthesis by increasing trehalose synthesis, which facilitated increased desiccation tolerance. Results obtained from flow cytometry using the membrane exclusion dye propidium iodide suggested that Hsp12p helped maintain plasma membrane integrity during desiccation. Analysis of the oxidative loads experienced by the wild-type and Δhsp12 strains showed that during mid-exponential phase, the increased trehalose levels present in the Δhsp12 cells resulted in increased protection of these cells against reactive oxygen species compared with wild-type cells. During stationary phase, lower levels of reactive oxygen species reduction by reduced glutathione was enhanced in the wild-type strain, which displayed lower intracellular trehalose concentrations. Comparison of the tolerance of the wild-type and Δhsp12 strains with applied oxidative stress showed that the Δhsp12 strain was more tolerant to exogenously applied H2O2, which we attributed to the higher intracellular trehalose concentration. Flow cytometry demonstrated that Hsp12p played a role in maintaining plasma membrane integrity during applied oxidative stress.

scholarly journals Bordetella pertussis Virulence Factors Affect Phagocytosis by Human Neutrophils

2000 ◽  
Vol 68 (3) ◽  
pp. 1735-1739 ◽  
Author(s):  
Christine L. Weingart ◽  
Alison A. Weiss
Keyword(s):  
Adenylate Cyclase ◽  
Virulence Factors ◽  
Pertussis Toxin ◽  
Bordetella Pertussis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Human Neutrophils ◽  
Wild Type ◽  
Dermonecrotic Toxin ◽  
Adenylate Cyclase Toxin

ABSTRACT The interaction between human neutrophils and wild-typeBordetella pertussis or mutants expressing altered lipopolysaccharide or lacking virulence factors—pertussis toxin, adenylate cyclase toxin, dermonecrotic toxin, filamentous hemagglutinin (FHA), pertactin, or BrkA—was examined. In the absence of antibodies, the wild-type strain and the mutants, with the exception of mutants lacking FHA, attached efficiently to neutrophils. The addition of opsonizing antibodies caused a significant reduction (approximately 50%) in attachment of the wild-type strain and most of the mutants expressing FHA, suggesting that bacterium-mediated attachment is more efficient than Fc-mediated attachment. Phagocytosis was also examined. In the absence of antibodies, about 12% of the wild-type bacteria were phagocytosed. Opsonization caused a statistically significant reduction in phagocytosis (to 3%), possibly a consequence of reduced attachment. Phagocytosis of most of the mutants was similar to that of the wild type, with the exception of the mutants lacking adenylate cyclase toxin. About 70% of the adenylate cyclase toxin mutants were phagocytosed, but only in the presence of opsonizing antibody, suggesting that Fc receptor-mediated signaling may be needed for phagocytosis. These studies indicate that FHA mediates attachment ofB. pertussis to neutrophils, but adenylate cyclase toxin blocks phagocytosis.

In vitro Activities of Transition Metal Derivatives of Ketoconazole and Clotrimazole against a Wild Type Strain of Saccharomyces cerevisiae in Absence or Presence of Human Neutrophils

2011 ◽  
Vol 54 (11) ◽  
pp. 752-756
Author(s):  
Maribel Navarro ◽  
Ibis Colmenares ◽  
Heriberto Correia ◽  
Alexandra Hernández ◽  
Yelitza Ching ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transition Metal ◽  
Type Strain ◽  
Wild Type Strain ◽  
Human Neutrophils ◽  
Wild Type ◽  
Metal Derivatives ◽  
Derivatives Of

scholarly journals Effects of Mutations of RAD50, RAD51, RAD52, and Related Genes on Illegitimate Recombination in Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 142 (2) ◽  
pp. 383-391 ◽  
Author(s):  
Yasumasa Tsukamoto ◽  
Jun-ichi Kato ◽  
Hideo Ikeda
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Quantitative Analysis ◽  
Structural Analysis ◽  
Recombination Rate ◽  
Type Strain ◽  
Negative Selection ◽  
Wild Type Strain ◽  
Illegitimate Recombination ◽  
Wild Type ◽  
In The Wild

Abstract To examine the mechanism of illegitimate recombination in Saccharomyces cerevisiae, we have developed a plasmid system for quantitative analysis of deletion formation. A can1 cyh2 cell carrying two negative selection markers, the CAN1 and CYH2 genes, on a YCp plasmid is sensitive to canavanine and cycloheximide, but the cell becomes resistant to both drugs when the plasmid has a deletion over the CAN1 and CYH2 genes. Structural analysis of the recombinant plasmids obtained from the resistant cells showed that the plasmids had deletions at various sites of the CAN1-CYH2 region and there were only short regions of homology (1-5 bp) at the recombination junctions. The results indicated that the deletion detected in this system were formed by illegitimate recombination. Study on the effect of several rad mutations showed that the recombination rate was reduced by 30-, 10-, 10-, and 10-fold in the rad52, rad50, mre11, and xrs2 mutants, respectively, while in the rud51, 54, 55, and 57 mutants, the rate was comparable to that in the wild-type strain. The rad52 mutation did not affect length of homology at junction sites of illegitimate recombination.

scholarly journals The role of Zur-regulated lipoprotein A in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles in Acinetobacter baumannii

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nayeong Kim ◽  
Hyo Jeong Kim ◽  
Man Hwan Oh ◽  
Se Yeon Kim ◽  
Mi Hyun Kim ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Mutant Strain ◽  
Antimicrobial Susceptibility ◽  
Type Strain ◽  
Wild Type Strain ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Wild Type ◽  
Bacterial Morphology

Abstract Background Zinc uptake-regulator (Zur)-regulated lipoprotein A (ZrlA) plays a role in bacterial fitness and overcoming antimicrobial exposure in Acinetobacter baumannii. This study further characterized the zrlA gene and its encoded protein and investigated the roles of the zrlA gene in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles (OMVs) in A. baumannii ATCC 17978. Results In silico and polymerase chain reaction analyses showed that the zrlA gene was conserved among A. baumannii strains with 97–100% sequence homology. Recombinant ZrlA protein exhibited a specific enzymatic activity of D-alanine-D-alanine carboxypeptidase. Wild-type A. baumannii exhibited more morphological heterogeneity than a ΔzrlA mutant strain during stationary phase. The ΔzrlA mutant strain was more susceptible to gentamicin than the wild-type strain. Sizes and protein profiles of OMVs were similar between the wild-type and ΔzrlA mutant strains, but the ΔzrlA mutant strain produced 9.7 times more OMV particles than the wild-type strain. OMVs from the ΔzrlA mutant were more cytotoxic in cultured epithelial cells than OMVs from the wild-type strain. Conclusions The present study demonstrated that A. baumannii ZrlA contributes to bacterial morphogenesis and antimicrobial resistance, but its deletion increases OMV production and OMV-mediated host cell cytotoxicity.

scholarly journals FixJ family regulator AcfR of Azorhizobium caulinodans is involved in symbiosis with the host plant

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Wei Liu ◽  
Xue Bai ◽  
Yan Li ◽  
Haikun Zhang ◽  
Xiaoke Hu
Keyword(s):  
Signal Transduction ◽  
Host Plant ◽  
Type Strain ◽  
Wild Type Strain ◽  
Response Regulator ◽  
Azorhizobium Caulinodans ◽  
Wild Type ◽  
Response Regulators ◽  
Free Living ◽  
Two Component

Abstract Background A wide variety of bacterial adaptative responses to environmental conditions are mediated by signal transduction pathways. Two-component signal transduction systems are one of the predominant means used by bacteria to sense the signals of the host plant and adjust their interaction behaviour. A total of seven open reading frames have been identified as putative two-component response regulators in the gram-negative nitrogen-fixing bacteria Azorhizobium caulinodans ORS571. However, the biological functions of these response regulators in the symbiotic interactions between A. caulinodans ORS571 and the host plant Sesbania rostrata have not been elucidated to date. Results In this study, we identified and investigated a two-component response regulator, AcfR, with a phosphorylatable N-terminal REC (receiver) domain and a C-terminal HTH (helix-turn-helix) LuxR DNA-binding domain in A. caulinodans ORS571. Phylogenetic analysis showed that AcfR possessed close evolutionary relationships with NarL/FixJ family regulators. In addition, six histidine kinases containing HATPase_c and HisKA domains were predicted to interact with AcfR. Furthermore, the biological function of AcfR in free-living and symbiotic conditions was elucidated by comparing the wild-type strain and the ΔacfR mutant strain. In the free-living state, the cell motility behaviour and exopolysaccharide production of the ΔacfR mutant were significantly reduced compared to those of the wild-type strain. In the symbiotic state, the ΔacfR mutant showed a competitive nodule defect on the stems and roots of the host plant, suggesting that AcfR can provide A. caulinodans with an effective competitive ability for symbiotic nodulation. Conclusions Our results showed that AcfR, as a response regulator, regulates numerous phenotypes of A. caulinodans under the free-living conditions and in symbiosis with the host plant. The results of this study help to elucidate the involvement of a REC + HTH_LuxR two-component response regulator in the Rhizobium-host plant interaction.

scholarly journals Mab_3083c Is a Homologue of RNase J and Plays a Role in Colony Morphotype, Aggregation, and Sliding Motility of Mycobacterium abscessus

2021 ◽  
Vol 9 (4) ◽  
pp. 676
Author(s):  
Ting-Yu Liu ◽  
Sheng-Hui Tsai ◽  
Jenn-Wei Chen ◽  
Yu-Ching Wang ◽  
Shiau-Ting Hu ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Opportunistic Pathogen ◽  
Mycobacterium Abscessus ◽  
Colony Morphology ◽  
Clinical Strain ◽  
Immunocompromised Patients ◽  
Clinical Infection ◽  
Wild Type ◽  
Sliding Motility

Mycobacterium abscessus is an opportunistic pathogen causing human diseases, especially in immunocompromised patients. M. abscessus strains with a rough morphotype are more virulent than those with a smooth morphotype. Morphotype switch may occur during a clinical infection. To investigate the genes involved in colony morphotype switching, we performed transposon mutagenesis in a rough clinical strain of M. abscessus. A morphotype switching mutant (smooth) named mab_3083c::Tn was obtained. This mutant was found to have a lower aggregative ability and a higher sliding motility than the wild type strain. However, its glycopeptidolipid (GPL) content remained the same as those of the wild type. Complementation of the mutant with a functional mab_3083c gene reverted its morphotype back to rough, indicating that mab_3083c is associated with colony morphology of M. abscessus. Bioinformatic analyses showed that mab_3083c has a 75.4% identity in amino acid sequence with the well-characterized ribonuclease J (RNase J) of M. smegmatis (RNase JMsmeg). Complementation of the mutant with the RNase J gene of M. smegmatis also switched its colony morphology from smooth back to rough. These results suggest that Mab_3083c is a homologue of RNase J and involved in regulating M. abscessus colony morphotype switching.

scholarly journals Mutations of folC cause increased susceptibility to sulfamethoxazole in Mycobacterium tuberculosis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ruiqi Wang ◽  
Kun Li ◽  
Jifang Yu ◽  
Jiaoyu Deng ◽  
Yaokai Chen
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Clinical Isolates ◽  
Aminobenzoic Acid ◽  
Wild Type ◽  
Dihydropteroate Synthase ◽  
Expression Levels ◽  
Encoding Gene ◽  
Increased Susceptibility

AbstractPrevious studies showed that mutation of folC caused decreased expression of the dihydropteroate synthase encoding gene folP2 in Mycobacterium tuberculosis (M. tuberculosis). We speculated that mutation of folC in M. tuberculosis might affect the susceptibility to sulfamethoxazole (SMX). To prove this, 53 clinical isolates with folC mutations were selected and two folC mutants (I43A, I43T) were constructed based on M. tuberculosis H37Ra. The results showed that 42 of the 53 clinical isolates (79.2%) and the two lab-constructed folC mutants were more sensitive to SMX. To probe the mechanism by which folC mutations make M. tuberculosis more sensitive to SMX, folP2 was deleted in H37Ra, and expression levels of folP2 were compared between H37Ra and the two folC mutants. Although deletion of folP2 resulted in increased susceptibility to SMX, no difference in folP2 expression was observed. Furthermore, production levels of para-aminobenzoic acid (pABA) were compared between the folC mutants and the wild-type strain, and results showed that folC mutation resulted in decreased production of pABA. Taken together, we show that folC mutation leads to decreased production of pABA in M. tuberculosis and thus affects its susceptibility to SMX, which broadens our understanding of mechanisms of susceptibilities to antifolates in this bacterium.

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