The dlt Operon of Bacillus cereus Is Required for Resistance to Cationic Antimicrobial Peptides and for Virulence in Insects

ABSTRACT The dlt operon encodes proteins that alanylate teichoic acids, the major components of cell walls of gram-positive bacteria. This generates a net positive charge on bacterial cell walls, repulsing positively charged molecules and conferring resistance to animal and human cationic antimicrobial peptides (AMPs) in gram-positive pathogenic bacteria. AMPs damage the bacterial membrane and are the most effective components of the humoral immune response against bacteria. We investigated the role of the dlt operon in insect virulence by inactivating this operon in Bacillus cereus, which is both an opportunistic human pathogen and an insect pathogen. The ΔdltBc mutant displayed several morphological alterations but grew at a rate similar to that for the wild-type strain. This mutant was less resistant to protamine and several bacterial cationic AMPs, such as nisin, polymyxin B, and colistin, in vitro. It was also less resistant to molecules from the insect humoral immune system, lysozyme, and cationic AMP cecropin B from Spodoptera frugiperda. ΔdltBc was as pathogenic as the wild-type strain in oral infections of Galleria mellonella but much less virulent when injected into the hemocoels of G. mellonella and Spodoptera littoralis. We detected the dlt operon in three gram-negative genera: Erwinia (Erwinia carotovora), Bordetella (Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica), and Photorhabdus (the entomopathogenic bacterium Photorhabdus luminescens TT01, the dlt operon of which did not restore cationic AMP resistance in ΔdltBc ). We suggest that the dlt operon protects B. cereus against insect humoral immune mediators, including hemolymph cationic AMPs, and may be critical for the establishment of lethal septicemia in insects and in nosocomial infections in humans.

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Inhibition of Food-Related Pathogenic Bacteria by god-Transformed Penicillium nalgiovense Strains

Journal of Food Protection ◽

10.4315/0362-028x-62.8.940 ◽

1999 ◽

Vol 62 (8) ◽

pp. 940-943 ◽

Cited By ~ 5

Author(s):

ROLF GEISEN

Keyword(s):

Antibacterial Activity ◽

Inhibitory Activity ◽

Type Strain ◽

Salmonella Enteritidis ◽

Pathogenic Bacteria ◽

Wild Type Strain ◽

Antibacterial Effect ◽

Wild Type ◽

Penicillium Nalgiovense ◽

And Staphylococcus Aureus

Two strains of Penicillium nalgiovense, which carried the god gene of Aspergillus niger and had increased glucose oxidase (GOD) activity compared with the wild-type strain, were tested for their ability to suppress the growth of certain food-related pathogenic bacteria. In contrast to the wild type, which showed no antibacterial effect when grown in mixed culture with different bacteria, the two tranformed strains were highly antagonistic. The strain that expressed higher amounts of GOD in general had higher inhibitory activity. Both strains showed antibacterial activity against Listeria monocytogenes, Salmonella Enteritidis, and Staphylococcus aureus. The inhibitory activity was dependent on the glucose concentration in the medium. S. aureus was completely inhibited at 1% glucose in the presence of the higher GOD-producing transformant. In contrast, if arabinose was used as a carbon source, no inhibition occurred. If catalase was added to the medium, the inhibitory activity of the transformants was completely inactivated, indicating that the hydrogen peroxide produced was responsible for the antibacterial activity of the transformants.

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Role of Lung Epithelial Cells in Defense against Klebsiella pneumoniae Pneumonia

Infection and Immunity ◽

10.1128/iai.70.3.1075-1080.2002 ◽

2002 ◽

Vol 70 (3) ◽

pp. 1075-1080 ◽

Cited By ~ 41

Author(s):

Guadalupe Cortés ◽

Dolores Álvarez ◽

Carles Saus ◽

Sebastián Albertí

Keyword(s):

Epithelial Cells ◽

Klebsiella Pneumoniae ◽

Type Strain ◽

Pathogenic Bacteria ◽

Wild Type Strain ◽

Capsular Polysaccharide ◽

Defense Mechanism ◽

Lung Epithelial Cells ◽

Wild Type ◽

Lung Epithelial

ABSTRACT The airway epithelium represents a primary site for the entry of pathogenic bacteria into the lungs. It has been suggested for many respiratory pathogens, including Klebsiella pneumoniae, that adhesion and invasion of the lung epithelial cells is an early stage of the pneumonia process. We observed that poorly encapsulated K. pneumoniae clinical isolates and an isogenic unencapsulated mutant invaded lung epithelial cells more efficiently than highly encapsulated strains independent of the K type. By contrast, the unencapsulated mutant was completely avirulent in a mouse model of pneumonia, unlike the wild-type strain, which produced pneumonia and systemic infection. Furthermore, the unencapsulated mutant bound more epithelially produced complement component C3 than the wild-type strain. Our results show that lung epithelial cells play a key role as a host defense mechanism against K. pneumoniae pneumonia, using two different strategies: (i) ingestion and control of the microorganisms and (ii) opsonization of the microorganisms. Capsular polysaccharide avoids both mechanisms and enhances the virulence of K. pneumoniae.

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Enhancing Isoprene Production by Genetic Modification of the 1-Deoxy-d-Xylulose-5-Phosphate Pathway inBacillus subtilis

Applied and Environmental Microbiology ◽

10.1128/aem.02341-10 ◽

2011 ◽

Vol 77 (7) ◽

pp. 2399-2405 ◽

Cited By ~ 70

Author(s):

Junfeng Xue ◽

Birgitte K. Ahring

Keyword(s):

Sigma Factor ◽

Type Strain ◽

Wild Type Strain ◽

Stress Factors ◽

Alternative Sigma Factor ◽

Wild Type ◽

Gram Positive ◽

Gram Positive Bacteria ◽

Overexpression Strain ◽

As Stress

ABSTRACTTo enhance the production of isoprene, a volatile 5-carbon hydrocarbon, in the Gram-positive spore-forming rod-shaped bacteriumBacillus subtilis, 1-deoxy-d-xylulose-5-phosphate synthase (Dxs) and 1-deoxy-d-xylulose-5-phosphate reductoisomerase (Dxr) were overexpressed inB. subtilisDSM 10. For the strain that overexpresses Dxs, the yield of isoprene was increased 40% over that by the wild-type strain. In the Dxr overexpression strain, the level of isoprene production was unchanged. Overexpression of Dxr together with Dxs showed an isoprene production level similar to that of the Dxs overproduction strain. The effects of external factors, such as stress factors including heat (48°C), salt (0.3 M NaCl), ethanol (1%), and oxidative (0.005% H2O2) stress, on isoprene production were further examined. Heat, salt, and H2O2induced isoprene production; ethanol inhibited isoprene production. In addition, induction and repression effects are independent of SigB, which is the general stress-responsive alternative sigma factor of Gram-positive bacteria.

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Pathogenic potential of a collagenase gene fromAeromonas veronii

Canadian Journal of Microbiology ◽

10.1139/w07-109 ◽

2008 ◽

Vol 54 (1) ◽

pp. 1-10 ◽

Cited By ~ 22

Author(s):

Hyun-Ja Han ◽

Tatsuo Taki ◽

Hidehiro Kondo ◽

Ikuo Hirono ◽

Takashi Aoki

Keyword(s):

Mutant Strain ◽

Type Strain ◽

Pathogenic Bacteria ◽

Wild Type Strain ◽

Collagenolytic Activity ◽

Bacterial Cells ◽

Wild Type ◽

Pathogenic Potential ◽

Collagenase Gene

The role of collagenase as a mechanism of bacterial pathogenicity in some pathogenic bacteria has been reported. The information on the role of collagenase in Aeromonas spp. pathogenesis is scant. In the present study, a mutant Aeromonas veronii RY001 that is deficient in the putative collagenase gene acg was constructed and compared with the wild-type strain for virulence factors. Bacterial cells and cell-free extracellular products of the mutant had significantly less collagenolytic activity, but there were not significant differences in caseinolytic, gelatinolytic, and elastolytic activities. Adhesion and invasion abilities of the mutant strain on epithelioma papillosum of carp cells was only 56% of that of the wild-type strain, and the cytotoxicity of the mutant strain to epithelioma papillosum of carp cells was only 42% of that of the wild-type strain. The LD50values of the wild-type strain were determined as 1.6 × 106and 3.5 × 105cfu in goldfish and mice, respectively, whereas the mutant RY001 strain showed slightly higher values (i.e., 2.8 × 106and 1.4 × 106cfu in goldfish and mice, respectively). These results indicated the involvement of the collagenase gene in the pathogenesis of A. veronii.

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Tagging Morphogenetic Genes by Insertional Mutagenesis in the Yeast Yarrowia lipolytica

Journal of Bacteriology ◽

10.1128/jb.183.10.3098-3107.2001 ◽

2001 ◽

Vol 183 (10) ◽

pp. 3098-3107 ◽

Cited By ~ 34

Author(s):

Mathias Richard ◽

Raymundo Rosas Quijano ◽

Samira Bezzate ◽

Florence Bordon-Pallier ◽

Claude Gaillardin

Keyword(s):

Saccharomyces Cerevisiae ◽

Yarrowia Lipolytica ◽

Cell Walls ◽

Type Strain ◽

Insertional Mutagenesis ◽

Wild Type Strain ◽

Wild Type ◽

Calcofluor White ◽

Hyphal Formation ◽

Yeast Yarrowia Lipolytica

ABSTRACT The yeast Yarrowia lipolytica is distantly related to Saccharomyces cerevisiae, can be genetically modified, and can grow in both haploid and diploid states in either yeast, pseudomycelial, or mycelial forms, depending on environmental conditions. Previous results have indicated that the STEand RIM pathways, which mediate cellular switching in other dimorphic yeasts, are not required for Y. lipolytica morphogenesis. To identify the pathways involved in morphogenesis, we mutagenized a wild-type strain of Y. lipolytica with a Tn3 derivative. We isolated eight tagged mutants, entirely defective in hyphal formation, from a total of 40,000 mutants and identified seven genes homologous toS. cerevisiae CDC25, RAS2, BUD6, KEX2, GPI7, SNF5, andPPH21. We analyzed their abilities to invade agar and to form pseudomycelium or hyphae under inducing conditions and their sensitivity to temperature and to Calcofluor white. Chitin staining was used to detect defects in their cell walls. Our results indicate that a functional Ras-cyclic AMP pathway is required for the formation of hyphae in Y. lipolytica and that perturbations in the processing of extracellular, possibly parietal, proteins result in morphogenetic defects.

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Methionine Sulfoxide Reductase A (MsrA) Deficiency Affects the Survival of Mycobacterium smegmatis within Macrophages

Journal of Bacteriology ◽

10.1128/jb.186.11.3590-3598.2004 ◽

2004 ◽

Vol 186 (11) ◽

pp. 3590-3598 ◽

Cited By ~ 58

Author(s):

T. Douglas ◽

D. S. Daniel ◽

B. K. Parida ◽

C. Jagannath ◽

S. Dhandayuthapani

Keyword(s):

Mutant Strain ◽

Mycobacterium Smegmatis ◽

Type Strain ◽

Pathogenic Bacteria ◽

Wild Type Strain ◽

Methionine Sulfoxide ◽

Intracellular Survival ◽

Methionine Sulfoxide Reductase ◽

Wild Type ◽

Methionine Sulfoxide Reductase A

ABSTRACT Methionine sulfoxide reductase A (MsrA) is an antioxidant repair enzyme which reduces oxidized methionine to methionine. Since oxidation of methionine in proteins impairs their function, an absence of MsrA leads to abnormalities in different organisms, including alterations in the adherence patterns and in vivo survival of certain pathogenic bacteria. To understand the role of MsrA in intracellular survival of bacteria, we disrupted the gene encoding MsrA in Mycobacterium smegmatis through homologous recombination. The msrA mutant strain of M. smegmatis exhibited significantly reduced intracellular survival in murine J774A.1 macrophages compared to the survival of its wild-type counterpart. Furthermore, immunofluorescence and immnunoblotting of phagosomes containing M. smegmatis strains revealed that the phagosomes with the msrA mutant strain acquired both p67phox of phagocyte NADPH oxidase and inducible nitric oxide synthase much earlier than the phagosomes with the wild-type strain. In addition, the msrA mutant strain of M. smegmatis was observed to be more sensitive to hydroperoxides than the wild-type strain was in vitro. These results suggest that MsrA plays an important role in both extracellular and intracellular survival of M. smegmatis.

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Antibody Responses 3-5 Months Post-Vaccination with mRNA-1273 or BNT163b2 in Nursing Home Residents

10.1101/2021.08.17.21262152 ◽

2021 ◽

Cited By ~ 1

Author(s):

Jessica A. Breznik ◽

Ali Zhang ◽

Angela Huynh ◽

Matthew S. Miller ◽

Ishac Nazy ◽

...

Keyword(s):

Immune Response ◽

Nursing Home ◽

Humoral Immune Response ◽

Type Strain ◽

Wild Type Strain ◽

Nursing Home Residents ◽

Wild Type ◽

Humoral Immune ◽

Fold Reduction ◽

Antibody Levels

AbstractNursing home residents often fail to mount robust responses to vaccinations and recent reports of breakthrough infections, particularly from variants of concern, raise questions about whether vaccination regimens elicit a sufficient humoral immune response or if booster doses are warranted. We examined SARS-CoV-2 antibody levels and neutralizing capacity in nursing home residents 3-5 months after 2 doses of mRNA-1273 or BNT163b2 vaccination as per recommended schedules.Nursing home residents were recruited from eight long-term care homes in Ontario, Canada, between March and July 2021. Antibody levels and neutralization capacity from a previously published convalescent cohort were used as a comparator. Serum SARS-CoV-2 IgA/G/M against spike (S) protein and its receptor-binding domain (RBD) were measured by validated ELISA, with assay cut-off at the mean and 3 standard deviations of a pre-COVID-19 population from the same geographic region. Antibody neutralization was measured against the wild-type strain of SARS-CoV-2 and the beta variant of concern (B.1.351).No neutralizing antibodies were detected in ∼20% of residents to the wild-type virus (30/155; 19%) or beta variant (27/134; 20%). Residents that received BNT163b2 had a ∼4-fold reduction in neutralization to the wild-type strain, and a ∼2-fold reduction in neutralization to the beta variant relative to those who received mRNA-1273.Current mRNA SARS-CoV-2 vaccine regimens may not have equivalent efficacy in nursing home residents. Our findings imply that differences in the humoral immune response may contribute to breakthrough infections, and suggest that consideration of the type of vaccine administered to older adults will have a positive impact on the generation of protective immunity.

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Enhancement of surfactin production of Bacillus subtilis fmbR by replacement of the native promoter with the Pspac promoter

Canadian Journal of Microbiology ◽

10.1139/w09-044 ◽

2009 ◽

Vol 55 (8) ◽

pp. 1003-1006 ◽

Cited By ~ 22

Author(s):

Huigang Sun ◽

Xiaomei Bie ◽

Fengxia Lu ◽

Yaping Lu ◽

Yundailai Wu ◽

...

Keyword(s):

Bacillus Subtilis ◽

Bacillus Cereus ◽

Type Strain ◽

Wild Type Strain ◽

Inducible Promoter ◽

Type B ◽

Wild Type ◽

Native Promoter ◽

Surfactin Production

Bacillus subtilis fmbR-1 was obtained from wild-type B. subtilis fmbR by replacement of the native promoter of the surfactin operon with the inducible promoter Pspac. The recombinant B. subtilis fmbR-1 produced more antibacterial substances than the wild-type strain. The overproducing phenotype was related to the enhancement of antagonistic activities against Bacillus cereus . HPLC peaks of surfactin for recombinant fmbR-1 showed patterns of lipopeptides similar to those of the wild-type strain, and surfactin production of the recombinant fmbR-1 was up to about fivefold greater than that of the wild-type strain without induction by isopropyl β-d-1-thiogalactopyranoside. However, the production of surfactin increased to about 10-fold more than that of the wild-type strain when it was induced by isopropyl β-d-1-thiogalactopyranoside.

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PorA Represents the Major Cell Wall Channel of the Gram-Positive Bacterium Corynebacterium glutamicum

Journal of Bacteriology ◽

10.1128/jb.185.16.4779-4786.2003 ◽

2003 ◽

Vol 185 (16) ◽

pp. 4779-4786 ◽

Cited By ~ 29

Author(s):

Noelia Costa-Riu ◽

Andreas Burkovski ◽

Reinhard Krämer ◽

Roland Benz

Keyword(s):

Cell Wall ◽

Corynebacterium Glutamicum ◽

Mutant Strain ◽

Type Strain ◽

Wild Type Strain ◽

Deletion Strain ◽

Wild Type ◽

Positive Bacterium ◽

Gram Positive ◽

Reverse Transcription Pcr

ABSTRACT The cell wall of the gram-positive bacterium Corynebacterium glutamicum contains a channel (porin) for the passage of hydrophilic solutes. The channel-forming polypeptide PorA is a 45-amino-acid acidic polypeptide with an excess of four negatively charged amino acids, which is encoded by the 138-bp gene porA. porA was deleted from the chromosome of C.glutamicum wild-type strain ATCC 13032 to obtain mutant ATCC 13032ΔporA. Southern blot analysis demonstrated that porA was deleted. Lipid bilayer experiments revealed that PorA was not present in the cell wall of the mutant strain. Searches within the known chromosome of C. glutamicum by using National Center for Biotechnology Information BLAST and reverse transcription-PCR showed that no other PorA-like protein is encoded on the chromosome or is expressed in the deletion strain. The porA deletion strain exhibited slower growth and longer growth times than the C. glutamicum wild-type strain. Experiments with different antibiotics revealed that the susceptibility of the mutant strain was much lower than that of the wild-type C. glutamicum strain. The results presented here suggest that PorA represents a major hydrophilic pathway through the cell wall and that C. glutamicum contains cell wall channels which are not related to PorA.

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