Genetic studies have implicated the HOG (High Osmolarity Glycerol response) pathway in the regulation of pathogenicity in Aspergillus fumigatus (an SEM image of the wild-type strain is shown; 4000 x). See the article by Winkelströter et al. on pp. 42-54 o

ABSTRACT Conidiation (asexual sporulation) is a key developmental process in filamentous fungi. We examined the gene regulatory roles of the Aspergillus fumigatus developmental transcription factors StuAp and BrlAp during conidiation. Conidiation was completely abrogated in an A. fumigatus ΔbrlA mutant and was severely impaired in a ΔstuA mutant. We determined the full genome conidiation transcriptomes of wild-type and ΔbrlA and ΔstuA mutant A. fumigatus and found that BrlAp and StuAp governed overlapping but distinct transcriptional programs. Six secondary metabolite biosynthetic clusters were found to be regulated by StuAp, while only one cluster exhibited BrlAp-dependent expression. The ΔbrlA mutant, but not the ΔstuA mutant, had impaired downregulation of genes encoding ribosomal proteins under nitrogen-limiting, but not carbon-limiting, conditions. Interestingly, inhibition of the target of rapamycin (TOR) pathway also caused downregulation of ribosomal protein genes in both the wild-type strain and the ΔbrlA mutant. Downregulation of these genes by TOR inhibition was associated with conidiation in the wild-type strain but not in the ΔbrlA mutant. Therefore, BrlAp-mediated repression of ribosomal protein gene expression is not downstream of the TOR pathway. Furthermore, inhibition of ribosomal protein gene expression is not sufficient to induce conidiation in the absence of BrlAp.

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A Point Mutation in the 14α-Sterol Demethylase Gene cyp51A Contributes to Itraconazole Resistance in Aspergillus fumigatus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.47.3.1120-1124.2003 ◽

2003 ◽

Vol 47 (3) ◽

pp. 1120-1124 ◽

Cited By ~ 204

Author(s):

T. M. Diaz-Guerra ◽

E. Mellado ◽

M. Cuenca-Estrella ◽

J. L. Rodriguez-Tudela

Keyword(s):

Amino Acid ◽

Aspergillus Fumigatus ◽

Point Mutation ◽

Resistant Strain ◽

Type Strain ◽

Wild Type Strain ◽

Gene Copy ◽

Wild Type ◽

Genes Encoding ◽

Resistant Strains

ABSTRACT The genes encoding 14α-sterol demethylases (cyp51A and cyp51B) were analyzed in 12 itraconazole (ITC)-resistant and three ITC-susceptible clinical isolates of Aspergillus fumigatus. Six ITC-resistant strains exhibited a substitution of another amino acid for glycine at position 54, which is located at a very conserved region of the Cyp51A protein. The cyp51A gene from the A. fumigatus wild-type strain (CM-237) was replaced with the mutated cyp51A gene copy of an ITC-resistant strain (AF-72). Two transformants exhibited resistance to ITC, both of which had incorporated the mutated copy of the cyp51A gene.

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Catalases of Aspergillus fumigatus

Infection and Immunity ◽

10.1128/iai.71.6.3551-3562.2003 ◽

2003 ◽

Vol 71 (6) ◽

pp. 3551-3562 ◽

Cited By ~ 153

Author(s):

Sophie Paris ◽

Deborah Wysong ◽

Jean-Paul Debeaupuis ◽

Kazutoshi Shibuya ◽

Bruno Philippe ◽

...

Keyword(s):

Metal Ions ◽

Aspergillus Fumigatus ◽

Alveolar Macrophages ◽

Type Strain ◽

Wild Type Strain ◽

Pathogenic Fungus ◽

Polymorphonuclear Neutrophils ◽

Wild Type ◽

Phagocytic Cells ◽

Increased Sensitivity

ABSTRACT Upon infection of a host, the pathogenic fungus Aspergillus fumigatus is attacked by the reactive oxygen species produced by phagocytic cells. Detoxification of hydrogen peroxide by catalases was proposed as a way to overcome this host response. A. fumigatus produces three active catalases; one is produced by conidia, and two are produced by mycelia. The mycelial catalase Cat1p was studied previously. Here we characterized the two other catalases, their genes, and the phenotypes of gene-disrupted mutants. CatAp, a spore-specific monofunctional catalase, is resistant to heat, metal ions, and detergent. This enzyme is a dimeric protein with 84.5-kDa subunits. The 749-amino-acid polypeptide exhibits high levels of similarity to the Aspergillus nidulans CatA catalase and to bacterial catalase HPII of Escherichia coli. In spite of increased sensitivity to H2O2, killing of ΔcatA conidia by alveolar macrophages and virulence in animals were similar to the killing of conidia by alveolar macrophages and virulence in animals observed for the wild type. In contrast to the Cat1p and CatAp catalases, the mycelial Cat2p enzyme is a bifunctional catalase-peroxidase and is sensitive to heat, metal ions, and detergent. This enzyme, an 82-kDa monomer, is homologous to catalase-peroxidases of several fungi and bacteria. Surprisingly, mycelium of the double Δcat1Δcat2 mutant with no catalase activity exhibited only slightly increased sensitivity to H2O2 and was as sensitive to killing by polymorphonuclear neutrophils as mycelium of the wild-type strain. However, this mutant exhibited delayed infection in the rat model of aspergillosis compared to infection by the wild-type strain. These results indicate that conidial catalase is not a virulence factor and that mycelial catalases transiently protect the fungus from the host.

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INTEGRATION EFFICIENCY IN DNA-INDUCED TRANSFORMATION OF PNEUMOCOCCUS. II. GENETIC STUDIES OF MUTANT INTEGRATING ALL THE MARKERS WITH A HIGH EFFICIENCY

Genetics ◽

10.1093/genetics/75.1.35 ◽

1973 ◽

Vol 75 (1) ◽

pp. 35-48

Author(s):

Gérard Tiraby ◽

Michel Armand Sicard

Keyword(s):

Ultraviolet Light ◽

Type Strain ◽

Wild Type Strain ◽

High Efficiency ◽

Wild Type ◽

Genetic Studies ◽

X Ray ◽

Reference Marker ◽

Low Efficiency ◽

Integration Efficiency

ABSTRACT Transformation of the pneumococcus mutant 401 by DNA's bearing the standard reference marker and several other markers belonging to two unlinked loci has shown that differences in the integration efficiencies of these markers were considerably reduced in this strain compared to the wild-type strain Cl 3. The sensitivities of mutant 401 to ultraviolet light and to X-ray irradiation are the same as those of Cl 3. However, in 401 all the markers tested are more resistant to inactivation as shown by transformation of 401 and Cl 3 by ultraviolet-irradiated DNA. The increase in resistance is greater for low efficiency (LE) markers than for high efficiency (HE) markers.—The decreased discrimination between LE and HE markers in strain 401 is not due to a mechanism related to modification of markers in the transforming DNA by the recipient cells, nor are the proteins inducing competence of the cells responsible for the differences in the integration efficiencies of various markers.—Genetic studies of the fate of recombinants as well as the measure of the amount of DNA taken up have shown that all the markers are integrated in strain 401 by the same recombination process, that specific to high efficiency markers.

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Substitutions at Methionine 220 in the 14α-Sterol Demethylase (Cyp51A) of Aspergillus fumigatus Are Responsible for Resistance In Vitro to Azole Antifungal Drugs

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.48.7.2747-2750.2004 ◽

2004 ◽

Vol 48 (7) ◽

pp. 2747-2750 ◽

Cited By ~ 150

Author(s):

E. Mellado ◽

G. Garcia-Effron ◽

L. Alcazar-Fuoli ◽

M. Cuenca-Estrella ◽

J. L. Rodriguez-Tudela

Keyword(s):

Sequence Analysis ◽

Aspergillus Fumigatus ◽

Type Strain ◽

Wild Type Strain ◽

Antifungal Drugs ◽

Clinical Isolates ◽

Wild Type ◽

Resistance Phenotype

ABSTRACT Five clinical isolates of Aspergillus fumigatus that exhibited similar patterns of reduced susceptibility to itraconazole and other triazole drugs were analyzed. Sequence analysis of genes (cyp51A and cyp51B) encoding the 14α-sterol demethylases revealed that all five strains harbored mutations in cyp51A resulting in the replacement of methionine at residue 220 by valine, lysine, or threonine. When the mutated cyp51A genes were introduced into an A. fumigatus wild-type strain, the transformants exhibited reduced susceptibility to all triazole agents, confirming that the mutations were responsible for the resistance phenotype.

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Targeted Gene Disruption of the 14-α Sterol Demethylase (cyp51A) in Aspergillus fumigatus and Its Role in Azole Drug Susceptibility

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.49.6.2536-2538.2005 ◽

2005 ◽

Vol 49 (6) ◽

pp. 2536-2538 ◽

Cited By ~ 85

Author(s):

E. Mellado ◽

G. Garcia-Effron ◽

M. J. Buitrago ◽

L. Alcazar-Fuoli ◽

M. Cuenca-Estrella ◽

...

Keyword(s):

Aspergillus Fumigatus ◽

Type Strain ◽

Gene Disruption ◽

Wild Type Strain ◽

Drug Susceptibility ◽

Wild Type ◽

Targeted Disruption ◽

Targeted Gene Disruption ◽

Resistant Strains

ABSTRACT The role of Aspergillus fumigatus 14α-sterol demethylase (Cyp51A) in azole drug susceptibility was assessed. Targeted disruption of cyp51A in azole-susceptible and -resistant strains decreased MICs from 2- to 40-fold. The cyp51A mutants were morphologically indistinguishable from the wild-type strain, retaining the ability to cause pulmonary disease in neutropenic mice.

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

Genetics ◽

10.1093/genetics/142.2.383 ◽

1996 ◽

Vol 142 (2) ◽

pp. 383-391 ◽

Cited By ~ 2

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.

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

BMC Microbiology ◽

10.1186/s12866-020-02083-0 ◽

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.

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

BMC Microbiology ◽

10.1186/s12866-021-02138-w ◽

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.

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

Microorganisms ◽

10.3390/microorganisms9040676 ◽

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.

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