scholarly journals Transcriptomics-Aided Dissection of the Intracellular and Extracellular Roles of Microcystin in Microcystis aeruginosa PCC 7806

2014 ◽  
Vol 81 (2) ◽  
pp. 544-554 ◽  
Author(s):  
A. Katharina Makower ◽  
J. Merijn Schuurmans ◽  
Detlef Groth ◽  
Yvonne Zilliges ◽  
Hans C. P. Matthijs ◽  
...  
Keyword(s):  
Polyketide Synthase ◽  
Wild Type Strain ◽  
Carbon Limitation ◽  
Light Conditions ◽  
Wild Type ◽  
Low Light ◽  
Content Type ◽  
Expression Of Genes ◽  
Polyketide Synthase Gene

ABSTRACTRecent studies have provided evidence for both intracellular and extracellular roles of the potent hepatotoxin microcystin (MC) in the bloom-forming cyanobacteriumMicrocystis. Here, we surveyed transcriptomes of the wild-type strainM. aeruginosaPCC 7806 and the microcystin-deficient ΔmcyBmutant under low light conditions with and without the addition of external MC of the LR variant (MC-LR). Transcriptomic data acquired by microarray and quantitative PCR revealed substantial differences in the relative expression of genes of the central intermediary metabolism, photosynthesis, and energy metabolism. In particular, the data provide evidence for a lower photosystem I (PSI)-to-photosystem II (PSII) ratio and a more pronounced carbon limitation in the microcystin-deficient mutant. Interestingly, only 6% of the transcriptional differences could be complemented by external microcystin-LR addition. This MC signaling effect was seen exclusively for genes of the secondary metabolism category. The orphan polyketide synthase gene cluster IPF38-51 was specifically downregulated in response to external MC-LR under low light. Our data suggest a hierarchical and light-dependent cross talk of secondary metabolites and support both an intracellular and an extracellular role of MC inMicrocystis.

The Critical Role of Polyketide Synthase Gene On The Swainsonine Biosynthesis in The Fungus Metarhizium Anisopliae

2021 ◽  
Author(s):  
Lu Sun ◽  
Enxia Huang ◽  
Yu Zhang ◽  
Ziyu Guo ◽  
Kexin Wu ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Metarhizium Anisopliae ◽  
Type Strain ◽  
Polyketide Synthase ◽  
Wild Type Strain ◽  
Biosynthesis Pathway ◽  
Wild Type ◽  
Knock Out ◽  
Polyketide Synthase Gene

Abstract Swainsonine (SW) is the principal toxic ingredient of locoweeds, and is produced by fungi including Metarhizium anisopliae, Slafractonia leguminicola, and Alternaria oxytropis. While the SW biosynthesis pathway of fungi and the catalytic enzyme genes that regulate synthesis are not cleanly. In this study, we used homologous recombination (HR) to knock out and interfere with the polyketide synthase gene (pks) of M. anisopliae to determine its effect on the SW biosynthesis pathway. The concentration of SW was measured in the fermentation broth of M. anisopliae at 1 d, 2 d, 3 d, 4 d, 5 d, 6 d or 7 d using LC-MS. The gene for the pks gene was detected by RT-qPCR. Day 5 of M. anisopliae gave the highest content of SW and the highest expression of the pks gene. To determine the role of the pks gene in the SW biosynthesis pathway of M. anisopliae, we used PEG-mediated homologous recombination (HR) to transform a wild-type strain (WT) with a Benomyl (ben)-resistant fragment to knock out the pks gene producing a mutant-type strain (MT) and used PEG-mediated RNAi to transform a wild-type strain (WT) with a Benomyl (ben)-resistant plasmid to interfere with the pks gene. A complemented-type (CT) strain was produced by adding a complementation vector that contains the geneticin (G418) resistance gene as a marker. The content of SW didn’t detected in MT strain, and returned to the original level in the CT strain, while the content of SW was significantly decreased in RNAi strain. We suggest that mutation and RNAi in the pks gene affect the cell wall formation of M. anisopliae, while the colony diameters, phenotypes, and growth rates did not change significantly, and no obvious changes in other cellular organelles were noted. These results indicate that the pks gene plays a crucial role in the SW biosynthesis of M. anisopliae, which provides an important theoretical basis for illuminating the SW biosynthesis and solving locoism in livestock.

Identification of Crp as a novel regulator of the Std fimbrial expression in Salmonella

Microbiology ◽  
2021 ◽  
Author(s):  
Karine Dufresne ◽  
France Daigle
Keyword(s):  
Wild Type Strain ◽  
Distal Region ◽  
Transcriptional Factor ◽  
Major Influence ◽  
Wild Type ◽  
Content Type ◽  
Link Type ◽  
Serovar Typhimurium ◽  
Metabolic Regulators

The Salmonella enterica serovar Typhi genome contains 14 putative fimbrial systems. The Std fimbriae belong to the chaperone-usher family and its regulation has not been investigated in S. Typhi. Several regulators of Std were previously identified in the closely related serovar Typhimurium. We hypothesize that regulators of S. Typhimurium may be shared with S. Typhi, but that several other regulators remain to be discovered. Here, we describe the role of more than 50 different candidate regulators on std expression. Three types of regulators were investigated: known regulators in S. Typhimurium, in silico predicted regulators and virulence/metabolic regulators. Expression of std was determined in the regulator mutants and compared with the wild-type strain. Overall, 21 regulator mutations affect std promoter expression. The role of Crp, a newly identified factor for std expression, was further investigated. Crp acted as an activator of std expression on a distal region of the std promoter region. Together, our results demonstrate the major influence of Crp as a novel transcriptional factor on std promoter expression and later production of Std fimbriae in Salmonella .

scholarly journals Role of Aspergillus fumigatus DvrA in Host Cell Interactions and Virulence

2010 ◽  
Vol 9 (10) ◽  
pp. 1432-1440 ◽  
Author(s):  
Daniele E. Ejzykowicz ◽  
Norma V. Solis ◽  
Fabrice N. Gravelat ◽  
Josee Chabot ◽  
Xuexian Li ◽  
...  
Keyword(s):  
Epithelial Cell ◽  
Type Strain ◽  
Wild Type Strain ◽  
Host Cells ◽  
Epithelial Cell Line ◽  
Wild Type ◽  
Content Type ◽  
Pulmonary Epithelial Cell

ABSTRACT The transcription factors that regulate Aspergillus fumigatus interactions with host cells and virulence are incompletely defined. We investigated the role of the putative C2H2 transcription factor DvrA in governing these processes. Although DvrA was identified by its limited homology to Candida albicans Bcr1, a ΔdvrA mutant strain of A. fumigatus had wild-type adherence to host constituents in vitro. However, it had increased capacity to damage both endothelial cells and a pulmonary epithelial cell line compared to the ability of the wild-type strain and a ΔdvrA::dvrA-complemented strain. This increase in damage required direct contact between the mutant and host cells. The ΔdvrA mutant also stimulated greater CCL20, interleukin-8, and tumor necrosis factor mRNA expression in a pulmonary epithelial cell line compared to levels induced by the control strains. Also, it was resistant to nikkomycin Z, suggesting an altered cell wall composition. As predicted by these in vitro results, the ΔdvrA mutant had increased virulence and stimulated a greater pulmonary inflammatory response than the wild-type strain and ΔdvrA::dvrA-complemented strains in the nonneutropenic mouse model of invasive pulmonary aspergillosis. These results indicate that DvrA influences A. fumigatus virulence as well as its capacity to damage host cells and stimulate a proinflammatory response.

scholarly journals WhiB5, a Transcriptional Regulator That Contributes to Mycobacterium tuberculosis Virulence and Reactivation

2012 ◽  
Vol 80 (9) ◽  
pp. 3132-3144 ◽  
Author(s):  
Stefano Casonato ◽  
Axel Cervantes Sánchez ◽  
Hirohito Haruki ◽  
Monica Rengifo González ◽  
Roberta Provvedi ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Chronic Infection ◽  
Null Mutant ◽  
Wild Type ◽  
Secretion Systems ◽  
Content Type ◽  
Type Vii Secretion ◽  
Expression Of Genes ◽  
Genes Encoding

ABSTRACTThe proteins belonging to the WhiB superfamily are small global transcriptional regulators typical of actinomycetes. In this paper, we characterize the role of WhiB5, aMycobacterium tuberculosisprotein belonging to this superfamily. A null mutant was constructed inM. tuberculosisH37Rv and was shown to be attenuated during both progressive and chronic mouse infections. Mice infected with the mutant had smaller bacillary burdens in the lungs but a larger inflammatory response, suggesting a role of WhiB5 in immunomodulation. Most interestingly, thewhiB5mutant was not able to resume growth after reactivation from chronic infection, suggesting that WhiB5 controls the expression of genes involved in this process. The mutant was also more sensitive than the wild-type parental strain toS-nitrosoglutathione (GSNO) and was less metabolically active following prolonged starvation, underscoring the importance of GSNO and starvation in development and maintenance of chronic infection. DNA microarray analysis identified 58 genes whose expression is influenced by WhiB5, includingsigM, encoding an alternative sigma factor, and genes encoding the constituents of two type VII secretion systems, namely, ESX-2 and ESX-4.

scholarly journals Identification and Regulation offusA, the Polyketide Synthase Gene Responsible for Fusarin Production in Fusarium fujikuroi

2012 ◽  
Vol 78 (20) ◽  
pp. 7258-7266 ◽  
Author(s):  
Violeta Díaz-Sánchez ◽  
Javier Avalos ◽  
M. Carmen Limón
Keyword(s):  
Nitrogen Availability ◽  
Polyketide Synthase ◽  
High Sensitivity ◽  
Targeted Mutagenesis ◽  
Fusarium Fujikuroi ◽  
Mrna Levels ◽  
Wild Type ◽  
Sequence Comparisons ◽  
Content Type ◽  
Polyketide Synthase Gene

ABSTRACTFusarins are a class of mycotoxins of the polyketide family produced by differentFusariumspecies, including the gibberellin-producing fungusFusarium fujikuroi. Based on sequence comparisons between polyketide synthase (PKS) enzymes for fusarin production in otherFusariumstrains, we have identified theF. fujikuroiorthologue, calledfusA. The participation offusAin fusarin biosynthesis was demonstrated by targeted mutagenesis. Fusarin production is transiently stimulated by nitrogen availability in this fungus, a regulation paralleled by thefusAmRNA levels in the cell. Illumination of the cultures results in a reduction of the fusarin content, an effect partially explained by a high sensitivity of these compounds to light. Mutants of thefusAgene exhibit no external phenotypic alterations, including morphology and conidiation, except for a lack of the characteristic yellow and/or orange pigmentation of fusarins. Moreover, thefusAmutants are less efficient than the wild type at degrading cellophane on agar cultures, a trait associated with pathogenesis functions inFusarium oxysporum. ThefusAmutants, however, are not affected in their capacities to grow on plant tissues.

scholarly journals The Pathway-Specific Regulator ClaR of Streptomyces clavuligerus Has a Global Effect on the Expression of Genes for Secondary Metabolism and Differentiation

2015 ◽  
Vol 81 (19) ◽  
pp. 6637-6648 ◽  
Author(s):  
Yolanda Martínez-Burgo ◽  
Rubén Álvarez-Álvarez ◽  
Antonio Rodríguez-García ◽  
Paloma Liras
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Aerial Mycelium ◽  
Gene Clusters ◽  
Streptomyces Clavuligerus ◽  
Plasmid Copy Number ◽  
Wild Type ◽  
Plasmid Copy ◽  
Content Type ◽  
Expression Of Genes

ABSTRACTStreptomyces clavuligerusclaR::aphis aclaR-defective mutant, but in addition to itsclaRdefect it also carries fewer copies of the resident linear plasmids pSCL2 and pSCL4 (on the order of 4 × 105-fold lower than the wild-type strain), as shown by qPCR. To determine the function of ClaR without potential interference due to plasmid copy number, a new strain,S. clavuligerusΔclaR::aac, withclaRdeleted and carrying the wild-type level of plasmids, was constructed. Transcriptomic analyses were performed inS. clavuligerusΔclaR::aacandS. clavuligerusATCC 27064 as the control strain. The new ΔclaRmutant did not produce clavulanic acid (CA) and showed a partial expression of genes for the early steps of the CA biosynthesis pathway and a very poor expression (1 to 8%) of the genes for the late steps of the CA pathway. Genes for cephamycin C biosynthesis were weakly upregulated (1.7-fold at 22.5 h of culture) in the ΔclaRmutant, but genes for holomycin biosynthesis were expressed at levels from 3- to 572-fold higher than in the wild-type strain, supporting the observed overproduction of holomycin byS. clavuligerusΔclaR::aac. Interestingly, three secondary metabolites produced by gene clusters SMCp20, SMCp22, and SMCp24, encoding still-cryptic compounds, had partially or totally downregulated their genes in the mutant, suggesting a regulatory role for ClaR wider than previously reported. In addition, theamfRgene was downregulated, and consequently, the mutant did not produce aerial mycelium. Expression levels of about 100 genes in the genome were partially up- or downregulated in the ΔclaRmutant, many of them related to the upregulation of the sigma factor-encodingrpoEgene.

scholarly journals Virulence Traits of a Serogroup C Meningococcus and IsogeniccssAMutant, Defective in Surface-Exposed Sialic Acid, in a Murine Model of Meningitis

2019 ◽  
Vol 87 (4) ◽  
Author(s):  
Roberta Colicchio ◽  
Chiara Pagliuca ◽  
Susanna Ricci ◽  
Elena Scaglione ◽  
Denis Grandgirard ◽  
...  
Keyword(s):  
Sialic Acid ◽  
Corpus Callosum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Lethal Dose ◽  
Sialic Acids ◽  
Wild Type ◽  
Knockout Mutant ◽  
Content Type

ABSTRACTIn serogroup CNeisseria meningitidis, thecssA(siaA) gene codes for an UDP-N-acetylglucosamine 2-epimerase that catalyzes the conversion of UDP-N-acetyl-α-d-glucosamine intoN-acetyl-d-mannosamine and UDP in the first step in sialic acid biosynthesis. This enzyme is required for the biosynthesis of the (α2→9)-linked polysialic acid capsule and for lipooligosaccharide (LOS) sialylation. In this study, we have used a reference serogroup C meningococcal strain and an isogeniccssAknockout mutant to investigate the pathogenetic role of surface-exposed sialic acids in a model of meningitis based on intracisternal inoculation of BALB/c mice. Results confirmed the key role of surface-exposed sialic acids in meningococcal pathogenesis. The 50% lethal dose (LD50) of the wild-type strain 93/4286 was about four orders of magnitude lower than that of thecssAmutant. Compared to the wild-type strain, the ability of this mutant to replicate in brain and spread systemically was severely impaired. Evaluation of brain damage evidenced a significant reduction in cerebral hemorrhages in mice infected with the mutant in comparison with the levels in those challenged with the wild-type strain. Histological analysis showed the typical features of bacterial meningitis, including inflammatory cells in the subarachnoid, perivascular, and ventricular spaces especially in animals infected with the wild type. Noticeably, 80% of mice infected with the wild-type strain presented with massive bacterial localization and accompanying inflammatory infiltrate in thecorpus callosum, indicating high tropism of meningococci exposing sialic acids toward this brain structure and a specific involvement of thecorpus callosumin the mouse model of meningococcal meningitis.

scholarly journals Involvement of H-NS in Acinetobacter baumannii’s Natural Transformation

2021 ◽  
Author(s):  
Casin Le ◽  
Camila Pimentel ◽  
Marisel Romina Tuttobene ◽  
Tomás Subils ◽  
Jenny Escalante ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Wild Type Strain ◽  
Natural Transformation ◽  
Regulatory Elements ◽  
Wild Type ◽  
Regulation Of Expression ◽  
Expression Levels ◽  
Expression Of Genes ◽  
Foreign Dna

Most Acinetobacter baumannii strains are naturally competent. Although some information is available about factors that enhance or reduce the frequency of transformation of this bacterium, the regulatory elements and mechanisms are barely understood. In this article, we describe studies on the role of H-NS in the regulation of expression of genes related to natural competency and the ability to uptake foreign DNA. The expression levels of the natural transformation-related genes pilA, pilT, pilQ, comEA, comEC, comF, and drpA were significantly increased in a Δhns derivative of Acinetobacter baumannii A118. Complementation of the mutant with a recombinant plasmid harboring hns restored expression levels of six of these genes (pilT remained expressed at high levels) to those of the wild-type strain. The transformation frequency of the A. baumannii A118 Δhns strain was significantly higher than that of the wild-type. Similar, albeit not identical, effects occurred when hns was deleted from the hypervirulent A. baumannii AB5075 strain. Reduction of gene expression in a few cases was not as pronounced as to reach wild-type levels, and expression of comEA was enhanced further. In conclusion, the expression of all seven transformation-related genes was enhanced after deleting hns in A. baumannii A118 and AB5075, and these modifications are accompanied by an increase in the cells’ transformability. The results demonstrate a role of H-NS in A. baumannii’s natural competence.

scholarly journals The RNA Chaperone Hfq Promotes Fitness of Actinobacillus pleuropneumoniae during Porcine Pleuropneumonia

2013 ◽  
Vol 81 (8) ◽  
pp. 2952-2961 ◽  
Author(s):  
Sargurunathan Subashchandrabose ◽  
Rhiannon M. Leveque ◽  
Roy N. Kirkwood ◽  
Matti Kiupel ◽  
Martha H. Mulks
Keyword(s):  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Actinobacillus Pleuropneumoniae ◽  
Wild Type ◽  
Content Type ◽  
Porcine Pleuropneumonia ◽  
Porcine Lungs

ABSTRACTActinobacillus pleuropneumoniaeis the etiological agent of porcine pleuropneumonia, an economically important disease of pigs. Thehfqgene inA. pleuropneumoniae, encoding the RNA chaperone and posttranscriptional regulator Hfq, is upregulated during infection of porcine lungs. To investigate the role of thisin vivo-induced gene inA. pleuropneumoniae, anhfqmutant strain was constructed. Thehfqmutant was defective in biofilm formation on abiotic surfaces. The level ofpgaCtranscript, encoding the biosynthesis of poly-β-1,6-N-acetylglucosamine (PNAG), a major biofilm matrix component, was lower and PNAG content was 10-fold lower in thehfqmutant than in the wild-type strain. When outer membrane proteins were examined, cysteine synthase, implicated in resistance to oxidative stress and tellurite, was not found at detectable levels in the absence of Hfq. Thehfqmutant displayed enhanced sensitivity to superoxide generated by methyl viologen and tellurite. These phenotypes were readily reversed by complementation with thehfqgene expressed from its native promoter. The role of Hfq in the fitness ofA. pleuropneumoniaewas assessed in a natural host infection model. Thehfqmutant failed to colonize porcine lungs and was outcompeted by the wild-type strain (median competitive index of 2 × 10−5). Our data demonstrate that thein vivo-induced genehfqis involved in the regulation of PNAG-dependent biofilm formation, resistance to superoxide stress, and the fitness and virulence ofA. pleuropneumoniaein pigs and begin to elucidate the role of anin vivo-induced gene in the pathogenesis of pleuropneumonia.

scholarly journals Role of Mrx Fimbriae of Xenorhabdus nematophila in Competitive Colonization of the Nematode Host

2011 ◽  
Vol 77 (20) ◽  
pp. 7247-7254 ◽  
Author(s):  
Holly Snyder ◽  
Hongjun He ◽  
Heather Owen ◽  
Chris Hanna ◽  
Steven Forst
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Infective Juvenile ◽  
Xenorhabdus Nematophila ◽  
Wild Type ◽  
Content Type ◽  
Mutant Strains ◽  
Phenotypic Variant

ABSTRACTXenorhabdus nematophilaengages in mutualistic associations with the infective juvenile (IJ) stage of specific entomopathogenic nematodes. Mannose-resistant (Mrx) chaperone-usher-type fimbriae are produced when the bacteria are grown on nutrient broth agar (NB agar). The role of Mrx fimbriae in the colonization of the nematode host has remained unresolved. We show thatX. nematophilagrown on LB agar produced flagella rather than fimbriae. IJs propagated onX. nematophilagrown on LB agar were colonized to the same extent as those propagated on NB agar. Further, progeny IJs were normally colonized bymrxmutant strains that lacked fimbriae both when bacteria were grown on NB agar and when coinjected into the insect host with aposymbiotic nematodes. Themrxstrains were not competitively defective for colonization when grown in the presence of wild-type cells on NB agar. In addition, a phenotypic variant strain that lacked fimbriae colonized as well as the wild-type strain. In contrast, themrxstrains displayed a competitive colonization defectin vivo. IJ progeny obtained from insects injected with comixtures of nematodes carrying either the wild-type or themrxstrain were colonized almost exclusively with the wild-type strain. Likewise, when insects were coinjected with aposymbiotic IJs together with a comixture of the wild-type andmrxstrains, the resulting IJ progeny were predominantly colonized with the wild-type strain. These results revealed that Mrx fimbriae confer a competitive advantage during colonizationin vivoand provide new insights into the role of chaperone-usher fimbriae in the life cycle ofX. nematophila.

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