Natural Infection of Citronmelon with Acidovorax avenae subsp. citrulli

Citronmelon fruits (Citrullus lanatus var. citroides (Bailey) Mansf.) with lesions were collected from a cowpea field in Frio County, TX, in July 1997. The lesions were circular, necrotic, or water-soaked, approximately 3 mm in diameter, and did not extend into the flesh of the fruit. Nonfluorescent, gram-negative bacteria were consistently isolated from lesions. Six representative strains were identified as Acidovorax avenae subsp. citrulli (Aac), using Biolog GN MicroPlates and the MicroLog data base release 3.50 (0.533 to 0.813 similarity). Aac causes leaf and fruit lesions (bacterial fruit blotch, BFB) on watermelon (C. lanatus (Thunb.) Matsum. & Nakai). Strains were tested for pathogenicity on watermelon seedlings (cv. Royal Sweet) by daubing bacterial suspensions (approximately 108 CFU/ml) onto cotyledons of 1-week-old seedlings. Water soaking of cotyledons, followed by necrosis and seedling death, occurred within 5 days. These symptoms were indistinguishable from those caused by watermelon strains of Aac. Bacteria were reisolated from symptomatic seedlings. The source of the infection is not known. Watermelons had been grown in this field in 1996, but no BFB symptoms were observed. Citron fruit infected with Aac were found in nearby watermelon fields where BFB was present; the closest field was 50 m from the cowpea field. These observations suggest that citronmelon, a common weed in south Texas, has the potential to perpetuate Aac. This is the first documentation of a naturally occurring infection of citronmelon with Aac.

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IgG Responses to Porins and Lipopolysaccharide within an Outer Membrane-Based Vaccine against NontyphoidalSalmonellaDevelop at Discordant Rates

mBio ◽

10.1128/mbio.02379-17 ◽

2018 ◽

Vol 9 (2) ◽

Cited By ~ 9

Author(s):

Anna E. Schager ◽

C. Coral Dominguez-Medina ◽

Francesca Necchi ◽

Francesca Micoli ◽

Yun Shan Goh ◽

...

Keyword(s):

T Cell ◽

B Cell ◽

Outer Membrane ◽

Natural Infection ◽

Outer Membrane Vesicles ◽

Gram Negative Bacteria ◽

Igg Antibody ◽

Similar Frequency ◽

Gram Negative ◽

Bacterial Antigens

ABSTRACTAntibodies acquired after vaccination or natural infection with Gram-negative bacteria, such as invasiveSalmonella entericaserovar Typhimurium, can protect against disease. Immunization with naturally shed outer membrane vesicles from Gram-negative bacteria is being studied for its potential to protect against many infections, since antigens within vesicles maintain their natural conformation and orientation. Shedding can be enhanced through genetic modification, and the resulting particles, generalized modules for membrane antigens (GMMA), not only offer potential as vaccines but also can facilitate the study of B-cell responses to bacterial antigens. Here we show that the response to immunization with GMMA fromS. Typhimurium (STmGMMA) provides B-cell-dependent protection and induces antibodies to two immunodominant antigens, lipopolysaccharide (LPS) and porins. Antibodies to LPS O antigen (O-Ag) markedly enhance protection in the spleen, but this effect is less marked in the liver. Strikingly, IgG responses to LPS and porins develop with distinct kinetics. In the first week after immunization, there is a dramatic T-cell-independent B1b-cell-associated induction of all IgG isotypes, except IgG1, to porins but not to LPS. In contrast, production of IgG1 to either antigen was delayed and T cell dependent. Nevertheless, after 1 month, cells in the bone marrow secreting IgG against porins or LPS were present at a similar frequency. Unexpectedly, immunization with O-Ag-deficient STmGMMA did not substantially enhance the anti-porin response. Therefore, IgG switching to all antigens does not develop synchronously within the same complex and so the rate of IgG switching to a single component does not necessarily reflect its frequency within the antigenic complex.IMPORTANCEVaccines save millions of lives, yet for some infections there are none. This includes some types ofSalmonellainfections, killing hundreds of thousands of people annually. We show how a new type of vaccine, called GMMA, that is made from blebs shed from theSalmonellacell wall, works to protect against infection in mice by inducing host proteins (antibodies) specifically recognizing bacterial components (antigens). The rate of development of IgG antibody to antigens within GMMA occurred with different kinetics. However, the antibody response to GMMA persists and is likely to provide prolonged protection for those who need it. These results help show how antibody responses to bacterial antigens develop and how vaccines like GMMA can work and help prevent infection.

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Thanatin targets the intermembrane protein complex required for lipopolysaccharide transport inEscherichia coli

Science Advances ◽

10.1126/sciadv.aau2634 ◽

2018 ◽

Vol 4 (11) ◽

pp. eaau2634 ◽

Cited By ~ 33

Author(s):

Stefan U. Vetterli ◽

Katja Zerbe ◽

Maik Müller ◽

Matthias Urfer ◽

Milon Mondal ◽

...

Keyword(s):

Protein Interactions ◽

Macromolecular Complex ◽

Gram Negative Bacteria ◽

Periplasmic Protein ◽

Protein Protein Interactions ◽

Inner Membrane ◽

Gram Negative ◽

Research Priority ◽

Naturally Occurring ◽

Bacterial Outer Membrane

With the increasing resistance of many Gram-negative bacteria to existing classes of antibiotics, identifying new paradigms in antimicrobial discovery is an important research priority. Of special interest are the proteins required for the biogenesis of the asymmetric Gram-negative bacterial outer membrane (OM). Seven Lpt proteins (LptA to LptG) associate in most Gram-negative bacteria to form a macromolecular complex spanning the entire envelope, which transports lipopolysaccharide (LPS) molecules from their site of assembly at the inner membrane to the cell surface, powered by adenosine 5′-triphosphate hydrolysis in the cytoplasm. The periplasmic protein LptA comprises the protein bridge across the periplasm, which connects LptB2FGC at the inner membrane to LptD/E anchored in the OM. We show here that the naturally occurring, insect-derived antimicrobial peptide thanatin targets LptA and LptD in the network of periplasmic protein-protein interactions required to assemble the Lpt complex, leading to the inhibition of LPS transport and OM biogenesis inEscherichia coli.

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Increased severity of respiratory infections associated with elevated anti-LPS IgG2 which inhibits serum bactericidal killing

Journal of Experimental Medicine ◽

10.1084/jem.20132444 ◽

2014 ◽

Vol 211 (9) ◽

pp. 1893-1904 ◽

Cited By ~ 38

Author(s):

Timothy J. Wells ◽

Deborah Whitters ◽

Yanina R. Sevastsyanovich ◽

Jennifer N. Heath ◽

John Pravin ◽

...

Keyword(s):

Respiratory Infections ◽

Natural Infection ◽

Gram Negative Bacteria ◽

Inhibitory Antibody ◽

Gram Negative ◽

O Antigen ◽

Excess Production ◽

Blocking Antibodies ◽

Antigen Structure ◽

Induce Antibody

Although specific antibody induced by pathogens or vaccines is a key component of protection against infectious threats, some viruses, such as dengue, induce antibody that enhances the development of infection. In contrast, antibody-dependent enhancement of bacterial infection is largely unrecognized. Here, we demonstrate that in a significant portion of patients with bronchiectasis and Pseudomonas aeruginosa lung infection, antibody can protect the bacterium from complement-mediated killing. Strains that resist antibody-induced, complement-mediated killing produce lipopolysaccharide containing O-antigen. The inhibition of antibody-mediated killing is caused by excess production of O-antigen–specific IgG2 antibodies. Depletion of IgG2 to O-antigen restores the ability of sera to kill strains with long-chain O-antigen. Patients with impaired serum-mediated killing of P. aeruginosa by IgG2 have poorer respiratory function than infected patients who do not produce inhibitory antibody. We suggest that excessive binding of IgG2 to O-antigen shields the bacterium from other antibodies that can induce complement-mediated killing of bacteria. As there is significant sharing of O-antigen structure between different Gram-negative bacteria, this IgG2-mediated impairment of killing may operate in other Gram-negative infections. These findings have marked implications for our understanding of protection generated by natural infection and for the design of vaccines, which should avoid inducing such blocking antibodies.

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A Brief Review on New Naturally Occurring Cembranoid Diterpene Derivatives from the Soft Corals of the Genera Sarcophyton, Sinularia, and Lobophytum Since 2016

Molecules ◽

10.3390/molecules24040781 ◽

2019 ◽

Vol 24 (4) ◽

pp. 781 ◽

Cited By ~ 14

Author(s):

Inna Rodrigues ◽

Maria Miguel ◽

Wissem Mnif

Keyword(s):

Chemical Composition ◽

Biological Activities ◽

Biological Properties ◽

Gram Negative Bacteria ◽

Soft Corals ◽

Gram Negative ◽

Naturally Occurring ◽

Chemical Variability ◽

Bacteria And Fungi ◽

Almost All

This work reviews the new isolated cembranoid derivatives from species of the genera Sarcophyton, Sinularia, and Lobophytum as well as their biological properties, during 2016–2018. The compilation permitted to conclude that much more new cembranoid diterpenes were found in the soft corals of the genus Sarcophyton than in those belonging to the genera Lobophytum or Sinularia. Beyond the chemical composition, the biological properties were also reviewed, namely anti-microbial against several Gram-positive and Gram-negative bacteria and fungi, anti-inflammatory and anti-tumoral against several types of cancer cells. In spite of the biological activities detected in almost all samples, there is a remarkable diversity in the results which may be attributed to the chemical variability that needs to be deepened in order to develop new molecules with potential application in medicine.

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Evaluation of the API 20E system for identification of nonfermentative Gram-negative bacteria

Journal of Clinical Microbiology ◽

10.1128/jcm.7.6.539-545.1978 ◽

1978 ◽

Vol 7 (6) ◽

pp. 539-545 ◽

Cited By ~ 1

Author(s):

M Shayegani ◽

P S Maupin ◽

D M McGlynn

Keyword(s):

Data Base ◽

Conventional Method ◽

Close Agreement ◽

Acinetobacter Calcoaceticus ◽

Bordetella Bronchiseptica ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Complete Identification

The API 20E system for Enterobacteriaceae, recently broadened to include identification of nonfermentative gram-negative bacteria, was evaluated and compared with the conventional method for complete identification of 221 nonfermenters, which were well distributed into 48 species or biotypes and included organisms not listed in the API 20E data base. The results of 16 tests common to both systems were in close agreement. The API 20E system correctly identified 71 (43%) of the 165 organisms included in the API 20E data base. However, almost 90% of Acinetobacter calcoaceticus, three species of Pseudomonas, and Bordetella bronchiseptica were correctly identified to species.

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Digitalizing heterologous gene expression in Gram-negative bacteria with a portable on/off module

10.1101/783506 ◽

2019 ◽

Author(s):

Belén Calles ◽

Angel Goñi-Moreno ◽

Víctor de Lorenzo

Keyword(s):

Heterologous Gene Expression ◽

Host Bacterium ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Inducible Promoters ◽

E Coli ◽

Naturally Occurring ◽

Conditional Expression ◽

Colicin E3

ABSTRACTWhile prokaryotic promoters controlled by signal-responding regulators typically display a range of input/output ratios when exposed to cognate inducers, virtually no naturally occurring cases are known to have an off state of zero transcription—as ideally needed for synthetic circuits. To overcome this problem we have modelled and implemented simple digitalizer module that completely suppresses the basal level of otherwise strong promoters in such a way that expression in the absence of induction is entirely impeded. The circuit involves the interplay of a translation-inhibitory sRNA with the translational coupling of the gene of interest to a repressor such as LacI. The digitalizer module was validated with the strong inducible promoters Pm (induced by XylS in the presence of benzoate) and PalkB (induced by AlkS/dicyclopropylketone) and shown to perform effectively both in E. coli and the soil bacterium Pseudomonas putida. The distinct expression architecture allowed cloning and conditional expression of e.g. colicin E3, one molecule of which per cell suffices to kill the host bacterium. Revertants that escaped ColE3 killing were not found in hosts devoid of insertion sequences, suggesting that mobile elements are a major source of circuit inactivation in vivo.

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Cardiolipins Act as a Selective Barrier to Toll-Like Receptor 4 Activation in the Intestine

Applied and Environmental Microbiology ◽

10.1128/aem.00463-16 ◽

2016 ◽

Vol 82 (14) ◽

pp. 4264-4278 ◽

Cited By ~ 3

Author(s):

Stephen R. Coats ◽

Ahmed Hashim ◽

Nikolay A. Paramonov ◽

Thao T. To ◽

Michael A. Curtis ◽

...

Keyword(s):

Dietary Habits ◽

Significant Proportion ◽

Gram Negative Bacteria ◽

Toll Like Receptor ◽

Microbial Composition ◽

Toll Like Receptor 4 ◽

Gram Negative ◽

Content Type ◽

Naturally Occurring ◽

Intestinal Immune System

ABSTRACTIntestinal homeostasis mechanisms must protect the host intestinal tissue from endogenous lipopolysaccharides (LPSs) produced by the intestinal microbiota. In this report, we demonstrate that murine intestinal fecal lipids effectively block Toll-like receptor 4 (TLR4) responses to naturally occurringBacteroidetessp. LPS. Cardiolipin (CL) represents a significant proportion of the total intestinal and fecal lipids and, furthermore, potently antagonizes TLR4 activation by reducing LPS binding at the lipopolysaccharide binding protein (LBP), CD14, and MD-2 steps of the TLR4 signaling pathway. It is further demonstrated that intestinal lipids and CL are less effective at neutralizing more potentEnterobacteriaceae-type LPS, which is enriched in feces obtained from mice with dextran sodium sulfate (DSS)-treated inflammatory bowel disease. The selective inhibition of naturally occurring LPS structures by intestinal lipids may represent a novel homeostasis mechanism that blocks LPS activation in response to symbiotic but not dysbiotic microbial communities.IMPORTANCEThe guts of animals harbor a variety of Gram-negative bacteria associated with both states of intestinal health and states of disease. Environmental factors, such as dietary habits, can drive the microbial composition of the host animal's intestinal bacterial community toward a more pathogenic state. Both beneficial and harmful Gram-negative bacteria are capable of eliciting potentially damaging inflammatory responses from the host intestinal tissues via a lipopolysaccharide (LPS)-dependent pathway. Physical mucosal barriers and antibodies produced by the intestinal immune system protect against the undesired inflammatory effects of LPS, although it is unknown why some bacteria are more effective at overcoming the protective barriers than others. This report describes the discovery of a lipid-type protective barrier in the intestine that reduces the deleterious effects of LPSs from beneficial bacteria but is less effective in dampening the inflammatory effects of LPSs from harmful bacteria, providing a novel mechanistic insight into inflammatory intestinal disorders.

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Past and Present Perspectives on β-Lactamases

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01076-18 ◽

2018 ◽

Vol 62 (10) ◽

Cited By ~ 159

Author(s):

Karen Bush

Keyword(s):

Sequence Data ◽

Amino Acid Sequences ◽

Gram Negative Bacteria ◽

Gram Negative ◽

Penicillin Binding Proteins ◽

Gram Positive Bacteria ◽

Class A ◽

Naturally Occurring ◽

Clinical Community ◽

Sequencing Studies

ABSTRACTβ-Lactamases, the major resistance determinant for β-lactam antibiotics in Gram-negative bacteria, are ancient enzymes whose origins can be traced back millions of years ago. These well-studied enzymes, currently numbering almost 2,800 unique proteins, initially emerged from environmental sources, most likely to protect a producing bacterium from attack by naturally occurring β-lactams. Their ancestors were presumably penicillin-binding proteins that share sequence homology with β-lactamases possessing an active-site serine. Metallo-β-lactamases also exist, with one or two catalytically functional zinc ions. Although penicillinases in Gram-positive bacteria were reported shortly after penicillin was introduced clinically, transmissible β-lactamases that could hydrolyze recently approved cephalosporins, monobactams, and carbapenems later became important in Gram-negative pathogens. Nomenclature is based on one of two major systems. Originally, functional classifications were used, based on substrate and inhibitor profiles. A later scheme classifies β-lactamases according to amino acid sequences, resulting in class A, B, C, and D enzymes. A more recent nomenclature combines the molecular and biochemical classifications into 17 functional groups that describe most β-lactamases. Some of the most problematic enzymes in the clinical community include extended-spectrum β-lactamases (ESBLs) and the serine and metallo-carbapenemases, all of which are at least partially addressed with new β-lactamase inhibitor combinations. New enzyme variants continue to be described, partly because of the ease of obtaining sequence data from whole-genome sequencing studies. Often, these new enzymes are devoid of any phenotypic descriptions, making it more difficult for clinicians and antibiotic researchers to address new challenges that may be posed by unusual β-lactamases.

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Antibacterial activities of watermelon (Citrullus lanatus) rind and seed extracts against selected gram-positive and gram-negative bacteria

International Journal of Medical Toxicology & Legal Medicine ◽

10.5958/0974-4614.2020.00052.2 ◽

2020 ◽

Vol 23 (3and4) ◽

pp. 95-100

Author(s):

Mustafa Fadil Mohammed ◽

Hemah Banu Kannan ◽

Mohammed Abdalqader ◽

Mohanad Rahman Alwan ◽

Mohammed Abdelfatah Alhoot ◽

...

Keyword(s):

Citrullus Lanatus ◽

Antibacterial Activities ◽

Gram Negative Bacteria ◽

Gram Positive ◽

Gram Negative ◽

Seed Extracts

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First Report of Infection of Honeydew with Acidovorax avenae subsp. citrulli

Plant Disease ◽

10.1094/pdis.1997.81.6.694c ◽

1997 ◽

Vol 81 (6) ◽

pp. 694-694 ◽

Cited By ~ 29

Author(s):

T. Isakeit ◽

M. C. Black ◽

L. W. Barnes ◽

J. B. Jones

Keyword(s):

Cucumis Melo ◽

Gram Negative Bacteria ◽

Sterile Water ◽

Bacterial Strains ◽

First Report ◽

Bacterial Fruit Blotch ◽

Overhead Irrigation ◽

Center Pivot ◽

Diseased Fruit ◽

Biolog Gn

Honeydew fruits (Cucumis melo var. inodorus Jacq. ‘Morning Ice,’ ‘Honeybrew,’ and ‘Green Flesh’) with circular, 3- to 10-mm-diameter lesions that did not extend into the flesh of the fruit were collected from a field in Frio County, TX, in October 1996. Lesions were either water-soaked or had a scabby center with a water-soaked edge. Non-fluorescent, gram-negative bacteria were consistently isolated from lesions. Eleven representative bacterial strains had 0.835 to 0.950 similarity to Acidovorax avenae subsp. citrulli, using Biolog GN Microplates and the MicroLog data base release 3.50 (Biolog, Hayward, CA). Strains were tested for pathogenicity on watermelon (C. lanatus (Thunb.) Matsum. & Nakai ‘Royal Sweet’) and honeydew seedlings (cv. Morning Ice) by daubing suspensions (approximately 108 CFU/ml) of bacteria onto cotyledons of 1-week-old transplants. Water soaking, followed by necrosis, occurred after 3 to 5 days. A. avenae subsp. citrulli, the causal agent of bacterial fruit blotch of watermelon, was reisolated from lesions. Detached fruit of honeydew (various cultivars) and watermelon (cv. Emperor) were surface disinfested with 70% ethanol, injected sub-epidermally with bacterial suspensions in blemish-free areas, and incubated at 24°C. Water-soaked lesions developed on fruit 10 to 14 days later and the bacteria were reisolated from inoculated fruit. Fruit inoculated with sterile water did not develop symptoms. Female flowers of honeydew plants (cv. Honeybrew) were inoculated at the time of pollination with a suspension of bacteria daubed on the fruit surface. Pollinated fruits were sealed in a moist chamber for 48 h. Circular, water-soaked spots developed 10 to 14 days later. A. avenae subsp. citrulli was reisolated from these lesions. The affected 44-ha field utilized center pivot irrigation and the incidence of diseased fruit exceeded 50%. The source of the pathogen is unknown. Bacterial fruit blotch was identified in watermelon grown under overhead irrigation 0.8 km from this honeydew field 9 weeks earlier. In past years, bacterial fruit blotch has occurred in watermelon fields in Frio County (1). Honeydew from other fields in the vicinity, including one that was also sprinkler irrigated, did not show these symptoms. This is the first report of A. avenae subsp. citrulli causing a disease of honeydew fruit. Reference: M. C. Black et al. Plant Dis. 78:831, 1994.

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