Production ofN-acylhomoserine lactone signal molecules by gram-negative soil-borne and plant-associated bacteria

In gram-negative bacteria, many important changes in gene expression and behavior are regulated in a popula tion density-dependent fashion by N-acyl homoserine lac tone (AHL) signal molecules. Exudates from pea (Pisum sativum) seedlings were found to contain several separable activities that mimicked AHL signals in well-characterized bacterial reporter strains, stimulating AHL-regulated be haviors in some strains while inhibiting such behaviors in others. The chemical nature of the active mimic com pounds is currently unknown, but all extracted differently into organic solvents than common bacterial AHLs. Various species of higher plants in addition to pea were found to secrete AHL mimic activities. The AHL signal-mimic compounds could prove to be important in determining the outcome of interactions between higher plants and a diver sity of pathogenic, symbiotic, and saprophytic bacteria.

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Regulation of Plant Mineral Nutrition by Signal Molecules

Microorganisms ◽

10.3390/microorganisms9040774 ◽

2021 ◽

Vol 9 (4) ◽

pp. 774

Author(s):

Vipin Chandra Kalia ◽

Chunjie Gong ◽

Sanjay K. S. Patel ◽

Jung-Kul Lee

Keyword(s):

Signal Molecules ◽

Gram Negative Bacteria ◽

Human Beings ◽

High Cell ◽

Specific Chemical ◽

Gram Negative ◽

Plant Mineral Nutrition ◽

Recent Developments ◽

Cell Densities ◽

Metabolic Activities

Microbes operate their metabolic activities at a unicellular level. However, it has been revealed that a few metabolic activities only prove beneficial to microbes if operated at high cell densities. These cell density-dependent activities termed quorum sensing (QS) operate through specific chemical signals. In Gram-negative bacteria, the most widely reported QS signals are acylhomoserine lactones. In contrast, a novel QS-like system has been elucidated, regulating communication between microbes and plants through strigolactones. These systems regulate bioprocesses, which affect the health of plants, animals, and human beings. This mini-review presents recent developments in the QS and QS-like signal molecules in promoting plant health.

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Inhibition of Quorum Sensing in Serratia marcescens AS-1 by Synthetic Analogs of N-Acylhomoserine Lactone

Applied and Environmental Microbiology ◽

10.1128/aem.00593-07 ◽

2007 ◽

Vol 73 (20) ◽

pp. 6339-6344 ◽

Cited By ~ 80

Author(s):

Tomohiro Morohoshi ◽

Toshitaka Shiono ◽

Kiyomi Takidouchi ◽

Masashi Kato ◽

Norihiro Kato ◽

...

Keyword(s):

Quorum Sensing ◽

Serratia Marcescens ◽

Biofilm Formation ◽

Acyl Chain ◽

Regulatory System ◽

Homoserine Lactone ◽

Signal Molecule ◽

Swarming Motility ◽

Gram Negative ◽

Acylhomoserine Lactone

ABSTRACT Quorum sensing is a regulatory system for controlling gene expression in response to increasing cell density. N-Acylhomoserine lactone (AHL) is produced by gram-negative bacteria, which use it as a quorum-sensing signal molecule. Serratia marcescens is a gram-negative opportunistic pathogen which is responsible for an increasing number of serious nosocomial infections. S. marcescens AS-1 produces N-hexanoyl homoserine lactone (C6-HSL) and N-(3-oxohexanoyl) homoserine lactone and regulates prodigiosin production, swarming motility, and biofilm formation by AHL-mediated quorum sensing. We synthesized a series of N-acyl cyclopentylamides with acyl chain lengths ranging from 4 to 12 and estimated their inhibitory effects on prodigiosin production in AS-1. One of these molecules, N-nonanoyl-cyclopentylamide (C9-CPA), had a strong inhibitory effect on prodigiosin production. C9-CPA also inhibited the swarming motility and biofilm formation of AS-1. A competition assay revealed that C9-CPA was able to inhibit quorum sensing at four times the concentration of exogenous C6-HSL and was more effective than the previously reported halogenated furanone. Our results demonstrated that C9-CPA was an effective quorum-sensing inhibitor for S. marcescens AS-1.

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Interference with Pseudomonas aeruginosa Quorum Sensing and Virulence by the Mycobacterial Pseudomonas Quinolone Signal Dioxygenase AqdC in Combination with the N-Acylhomoserine Lactone Lactonase QsdA

Infection and Immunity ◽

10.1128/iai.00278-19 ◽

2019 ◽

Vol 87 (10) ◽

Cited By ~ 4

Author(s):

Franziska S. Birmes ◽

Ruth Säring ◽

Miriam C. Hauke ◽

Niklas H. Ritzmann ◽

Steffen L. Drees ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Virulence Factors ◽

Rhodococcus Erythropolis ◽

Quorum Quenching ◽

Signal Molecules ◽

Content Type ◽

Acylhomoserine Lactone ◽

Regulatory Effects ◽

Epithelial Lung Cells

ABSTRACT The nosocomial pathogen Pseudomonas aeruginosa regulates its virulence via a complex quorum sensing network, which, besides N-acylhomoserine lactones, includes the alkylquinolone signal molecules 2-heptyl-3-hydroxy-4(1H)-quinolone (Pseudomonas quinolone signal [PQS]) and 2-heptyl-4(1H)-quinolone (HHQ). Mycobacteroides abscessus subsp. abscessus, an emerging pathogen, is capable of degrading the PQS and also HHQ. Here, we show that although M. abscessus subsp. abscessus reduced PQS levels in coculture with P. aeruginosa PAO1, this did not suffice for quenching the production of the virulence factors pyocyanin, pyoverdine, and rhamnolipids. However, the levels of these virulence factors were reduced in cocultures of P. aeruginosa PAO1 with recombinant M. abscessus subsp. massiliense overexpressing the PQS dioxygenase gene aqdC of M. abscessus subsp. abscessus, corroborating the potential of AqdC as a quorum quenching enzyme. When added extracellularly to P. aeruginosa cultures, AqdC quenched alkylquinolone and pyocyanin production but induced an increase in elastase levels. When supplementing P. aeruginosa cultures with QsdA, an enzyme from Rhodococcus erythropolis which inactivates N-acylhomoserine lactone signals, rhamnolipid and elastase levels were quenched, but HHQ and pyocyanin synthesis was promoted. Thus, single quorum quenching enzymes, targeting individual circuits within a complex quorum sensing network, may also elicit undesirable regulatory effects. Supernatants of P. aeruginosa cultures grown in the presence of AqdC, QsdA, or both enzymes were less cytotoxic to human epithelial lung cells than supernatants of untreated cultures. Furthermore, the combination of both aqdC and qsdA in P. aeruginosa resulted in a decline of Caenorhabditis elegans mortality under P. aeruginosa exposure.

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Bacterial Cellulose Containing Combinations of Antimicrobial Peptides with Various QQ Enzymes as a Prototype of an “Enhanced Antibacterial” Dressing: In Silico and In Vitro Data

Pharmaceutics ◽

10.3390/pharmaceutics12121155 ◽

2020 ◽

Vol 12 (12) ◽

pp. 1155

Author(s):

Aysel Aslanli ◽

Ilya Lyagin ◽

Nikolay Stepanov ◽

Denis Presnov ◽

Elena Efremenko

Keyword(s):

Antimicrobial Peptides ◽

Bacterial Cellulose ◽

In Silico ◽

Antimicrobial Agents ◽

Penicillin Acylase ◽

Signal Molecules ◽

Bacterial Cells ◽

Gram Positive ◽

Gram Negative

To improve the action of already in use antibiotics or new antimicrobial agents against different bacteria, the development of effective combinations of antimicrobial peptides (AMPs) with enzymes that can quench the quorum (QQ) sensing of bacterial cells was undertaken. Enzymes hydrolyzing N-acyl homoserine lactones (AHLs) and peptides that are signal molecules of Gram-negative and Gram-positive bacterial cells, respectively, were estimated as “partners” for antibiotics and antimicrobial peptides in newly designed antimicrobial–enzymatic combinations. The molecular docking of six antimicrobial agents to the surface of 10 different QQ enzyme molecules was simulated in silico. This made it possible to choose the best variants among the target combinations. Further, bacterial cellulose (BC) was applied as a carrier for uploading such combinations to generally compose prototypes of effective dressing materials with morphology, providing good absorbance. The in vitro analysis of antibacterial activity of prepared BC samples confirmed the significantly enhanced efficiency of the action of AMPs (including polymyxin B and colistin, which are antibiotics of last resort) in combination with AHL-hydrolyzing enzymes (penicillin acylase and His6-tagged organophosphorus hydrolase) against both Gram-negative and Gram-positive cells.

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Small, Stable Shuttle Vectors Based on the Minimal pVS1 Replicon for Use in Gram-Negative, Plant-Associated Bacteria

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2000.13.2.232 ◽

2000 ◽

Vol 13 (2) ◽

pp. 232-237 ◽

Cited By ~ 263

Author(s):

Stephan Heeb ◽

Yoshifumi Itoh ◽

Takayuki Nishijyo ◽

Ursula Schnider ◽

Christoph Keel ◽

...

Keyword(s):

Escherichia Coli ◽

Environmental Conditions ◽

Cloning Vectors ◽

Associated Bacteria ◽

Gram Negative ◽

Shuttle Vectors ◽

Recombinant Plasmids

The minimal replicon of the Pseudomonas plasmid pVS1 was genetically defined and combined with the Escherichia coli p15A replicon, to provide a series of new, oligocopy cloning vectors (5.3 to 8.3 kb). Recombinant plasmids derived from these vectors were stable in growing and nongrowing cells of root-colonizing P. fluorescens strains incubated under different environmental conditions for more than 1 month.

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045 ANTIBIOTIC SUSCEPTIBILITY OF PLANT-ASSOCIATED BACTERIA

HortScience ◽

10.21273/hortsci.29.5.434c ◽

1994 ◽

Vol 29 (5) ◽

pp. 434c-434 ◽

Cited By ~ 5

Author(s):

Patricia M. Buckley ◽

Barbara M. Reed

Keyword(s):

Bacterial Growth ◽

Infected Plant ◽

Basic Information ◽

Ph Change ◽

Gram Positive ◽

Associated Bacteria ◽

Gram Negative ◽

Gram Positive Bacteria ◽

Antibiotic Susceptibilities ◽

Microbial Contaminants

Most bacteria isolated from persistently contaminated micropropagated mint plants were Gram-negative rods identified as xanthomonads, pseudomonads, and agrobacteria based on their cultural characteristics. A few Gram-positive, non-sporeforming bacteria were also found. Inhibition of bacterial growth by gentamicin and streptomycin was greater at pH 6.5 and pH 7.5 than at pH 5.5. Inhibition by rifampicin and Timentin was less affected by pH change. Pseudomonads were uniformly resistant to Timentin at all pH's and at levels up to 1000 μg/ml. Streptomycin at 500 μg/ml was bactericidal for the pseudomonads and Gram-positive bacteria while 1000 μg/ml was required to kill xanthomonads and agrobacteria. Minimal bactericidal concentrations for gentamicin varied widely, even within groups, and ranged from 10 μg/ml to >80 μg/ml for agrobacteria. These results emphasize a need to acquire basic information about the identities and antibiotic susceptibilities of microbial contaminants before attempting treatment of infected plant cultures.

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Dominance of Vibrio fischeri in Secreted Mucus outside the Light Organ of Euprymna scolopes: the First Site of Symbiont Specificity

Applied and Environmental Microbiology ◽

10.1128/aem.69.7.3932-3937.2003 ◽

2003 ◽

Vol 69 (7) ◽

pp. 3932-3937 ◽

Cited By ~ 66

Author(s):

Spencer V. Nyholm ◽

Margaret J. McFall-Ngai

Keyword(s):

Fluorescent Protein ◽

Vibrio Fischeri ◽

Signal Molecules ◽

Natural Seawater ◽

Gram Negative Bacteria ◽

Light Organ ◽

Bacterial Cells ◽

Euprymna Scolopes ◽

Gram Negative ◽

Green Fluorescent

ABSTRACT Previous studies of the Euprymna scolopes-Vibrio fischeri symbiosis have demonstrated that, during colonization, the hatchling host secretes mucus in which gram-negative environmental bacteria amass in dense aggregations outside the sites of infection. In this study, experiments with green fluorescent protein-labeled symbiotic and nonsymbiotic species of gram-negative bacteria were used to characterize the behavior of cells in the aggregates. When hatchling animals were exposed to 103 to 106 V. fischeri cells/ml added to natural seawater, which contains a mix of approximately 106 nonspecific bacterial cells/ml, V. fischeri cells were the principal bacterial cells present in the aggregations. Furthermore, when animals were exposed to equal cell numbers of V. fischeri (either a motile or a nonmotile strain) and either Vibrio parahaemolyticus or Photobacterium leiognathi, phylogenetically related gram-negative bacteria that also occur in the host's habitat, the symbiont cells were dominant in the aggregations. The presence of V. fischeri did not compromise the viability of these other species in the aggregations, and no significant growth of V. fischeri cells was detected. These findings suggested that dominance results from the ability of V. fischeri either to accumulate or to be retained more effectively within the mucus. Viability of the V. fischeri cells was required for both the formation of tight aggregates and their dominance in the mucus. Neither of the V. fischeri quorum-sensing compounds accumulated in the aggregations, which suggested that the effects of these small signal molecules are not critical to V. fischeri dominance. Taken together, these data provide evidence that the specificity of the squid-vibrio symbiosis begins early in the interaction, in the mucus where the symbionts aggregate outside of the light organ.

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