Biological Role of Xanthomonadin Pigments inXanthomonas campestris pv. Campestris

ABSTRACT Previous studies have indicated that the yellow pigments (xanthomonadins) produced by phytopathogenic Xanthomonasbacteria are unimportant during pathogenesis but may be important for protection against photobiological damage. We used a Xanthomonas campestris pv. campestris parent strain, single-site transposon insertion mutant strains, and chromosomally restored mutant strains to define the biological role of xanthomonadins. Although xanthomonadin mutant strains were comparable to the parent strain for survival when exposed to UV light; after their exposure to the photosensitizer toluidine blue and visible light, survival was greatly reduced. Chromosomally restored mutant strains were completely restored for survival in these conditions. Likewise, epiphytic survival of a xanthomonadin mutant strain was greatly reduced in conditions of high light intensity, whereas a chromosomally restored mutant strain was comparable to the parent strain for epiphytic survival. These results are discussed with respect to previous results, and a model for epiphytic survival of X. campestris pv. campestris is presented.

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Xanthomonas campestris pv. campestris Requires a Functional pigB for Epiphytic Survival and Host Infection

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.1998.11.6.466 ◽

1998 ◽

Vol 11 (6) ◽

pp. 466-475 ◽

Cited By ~ 42

Author(s):

A. R. Poplawsky ◽

W. Chun

Keyword(s):

Sodium Hypochlorite ◽

Parent Strain ◽

Xanthomonas Campestris ◽

Leaf Surface ◽

Natural Infection ◽

Insertion Mutation ◽

Experimental Conditions ◽

Host Infection ◽

Epiphytic Survival ◽

Xanthomonas Campestris Pv Campestris

When cauliflower plants (Brassica oleraceae) were misted with bacterial suspensions of Xanthomonas campestris pv. campestris (causal agent of black rot of cruciferous plants), two separate populations of the pathogen were associated with the leaves. Initially, bacteria removable by sonication and sensitive to sodium hypochlorite treatment predominated (easily removable epiphytic bacteria, EREB). However, after 2 weeks, bacteria not removable by sonication and insensitive to sodium hypochlorite treatment were dominant. Although the exact location of this second population of the pathogen was not determined, evidence is presented to support its location in protected sites on the leaf surface. pigB of this pathogen is required for production of extracellular polysaccharide (EPS), xanthomonadin pigments, and the diffusible signal molecule, DF (diffusible factor). DF can extracellularly restore EPS and xanthomonadin production to pigB mutant strains. Parent strain B-24 and pigB mutant strain B24-B2 were identical for in planta growth and symptomatology after artificial infection by injection in leaf mid-veins. Subsequently, X. campestris pv. campestris parent strain B-24, Tn3HoHo1 pigB insertion mutation strain B24-B2, chromosomally restored pigB mutation strain B24-B2R, and strain B24-79 with a Tn3HoHo1 insertion in an unrelated part of the genome were compared for epiphytic survival on, and natural infection of, cauliflower. After application, strains B-24, B24-B2R, and B24-79 all maintained leaf EREB populations of between approximately 3 and 6 (log [1 + CFU per g of fresh weight]) over a 3-week period, whereas B24-B2 populations fell to nearly undetectable levels. Plants sprayed with strains B-24, B24-B2R, and B24-79 averaged between 1.0 and 1.2 lesions, whereas those sprayed with B24-B2 averaged only 0.03 lesions per plant after 3 weeks. Differences in EREB population levels did not explain the observed differences in host infection frequencies, and the results indicated that strain B24-B2 was reduced in its ability to infect the host via the hydathodes, but unaffected in infection via wounds. When strains B-24 and B24-B2 were mixed in equal numbers and sprayed on plants together, B24-B2 epiphytic populations were intermediate between those of B-24 applied alone and B24-B2 applied alone. These results indicate that a functional pigB is required for epiphytic survival and natural host infection under the experimental conditions tested, and suggest that DF, xanthomonadins, and EPS could all be important for survival of this pathogen on the leaf surface, and/or for host infection.

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The InhA2 Metalloprotease of Bacillus thuringiensis Strain 407 Is Required for Pathogenicity in Insects Infected via the Oral Route

Journal of Bacteriology ◽

10.1128/jb.184.12.3296-3304.2002 ◽

2002 ◽

Vol 184 (12) ◽

pp. 3296-3304 ◽

Cited By ~ 85

Author(s):

Sinda Fedhila ◽

Patricia Nel ◽

Didier Lereclus

Keyword(s):

Bacillus Thuringiensis ◽

Mutant Strain ◽

Galleria Mellonella ◽

Oral Route ◽

Vital Role ◽

Zinc Metalloprotease ◽

Mutant Strains ◽

Zinc Binding Domain

ABSTRACT The entomopathogenic bacterium Bacillus thuringiensis is known to secrete a zinc metalloprotease (InhA) that specifically cleaves antibacterial peptides produced by insect hosts. We identified a second copy of the inhA gene, named inhA2, in B. thuringiensis strain 407 Cry−. The inhA2 gene encodes a putative polypeptide showing 66.2% overall identity with the InhA protein and harboring the zinc-binding domain (HEXXH), which is characteristic of the zinc-requiring metalloproteases. We used a transcriptional inhA2′-lacZ fusion to show that inhA2 expression is induced at the onset of the stationary phase and is overexpressed in a Spo0A minus background. The presence of a reverse Spo0A box in the promoter region of inhA2 suggests that Spo0A directly regulates the transcription of inhA2. To determine the role of the InhA and InhA2 metalloproteases in pathogenesis, we used allelic exchange to isolate single and double mutant strains for the two genes. Spores and vegetative cells of the mutant strains were as virulent as those of the parental strain in immunized Bombyx mori larvae infected by the intrahemocoelic route. Exponential phase cells of all the strains displayed the same in vitro potential for colonizing the vaccinated hemocoel. We investigated the synergistic effect of the mutant strain spores on the toxicity of Cry1C proteins against Galleria mellonella larvae infected via the oral pathway. The spores of ΔinhA2 mutant strain were ineffective in providing synergism whereas those of the ΔinhA mutant strain were not. These results indicate that the B. thuringiensis InhA2 zinc metalloprotease has a vital role in virulence when the host is infected via the oral route.

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Gene Targeting and Gene Transfer Studies of the Biological Role of the Plasminogen/Plasmin System

Thrombosis and Haemostasis ◽

10.1055/s-0038-1642716 ◽

1995 ◽

Vol 74 (01) ◽

pp. 429-436 ◽

Cited By ~ 38

Author(s):

Peter Carmeliet ◽

Désiré Collen

Keyword(s):

Gene Transfer ◽

Gene Targeting ◽

Biological Role

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From Organizations of Processes to Organisms and Other Biological Individuals

10.1093/oso/9780198779636.003.0010 ◽

2018 ◽

Author(s):

Argyris Arnellos

Keyword(s):

Multicellular Organism ◽

Collaborative Networks ◽

Biological Role ◽

Regulatory Processes ◽

Different Types ◽

Organizational Framework

The emphasis on the collaborative dimension of life overlooks the importance of biological individuals (conceived of as integrated, self-maintaining organizations) in the build-up of more complex collaborative networks in the course of evolution. This chapter proposes a process-based organizational ontology for biology, according to which the essential features of unicellular organismicality are captured by a self-maintaining organization of processes integrated by means of a special type of collaboration (realized through regulatory processes entailing an indispensable interdependence) between its constitutive and its interactive aspects. This ontology is then used to describe different types of collaborations among cells and to suggest the type that yields a multicellular organism. The proposed organizational framework enables us to critically assess hypercollaborative views of life, especially issues related to the distinction between biological individuals and organisms and between life and non-life, without however underestimating the central biological role of collaboration.

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Histone acetylation increases the solubility of chromatin and occurs sequentially over most of the chromatin. A novel model for the biological role of histone acetylation.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)34382-5 ◽

1982 ◽

Vol 257 (13) ◽

pp. 7336-7347 ◽

Cited By ~ 9

Author(s):

M Perry ◽

R Chalkley

Keyword(s):

Histone Acetylation ◽

Biological Role ◽

Novel Model

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RND Efflux Systems Contribute to Resistance and Virulence of Aliarcobacter butzleri

Antibiotics ◽

10.3390/antibiotics10070823 ◽

2021 ◽

Vol 10 (7) ◽

pp. 823

Author(s):

Cristiana Mateus ◽

Ana Rita Nunes ◽

Mónica Oleastro ◽

Fernanda Domingues ◽

Susana Ferreira

Keyword(s):

Oxidative Stress ◽

Human Serum ◽

Ethidium Bromide ◽

Biofilm Formation ◽

Bacterial Resistance ◽

Efflux Pumps ◽

Bacterial Virulence ◽

Relative Fitness ◽

Mutant Strains

Aliarcobacter butzleri is an emergent enteropathogen that can be found in a range of environments. This bacterium presents a vast repertoire of efflux pumps, such as the ones belonging to the resistance nodulation cell division family, which may be associated with bacterial resistance, as well as virulence. Thus, this work aimed to evaluate the contribution of three RND efflux systems, AreABC, AreDEF and AreGHI, in the resistance and virulence of A. butzleri. Mutant strains were constructed by inactivation of the gene that encodes the inner membrane protein of these systems. The bacterial resistance profile of parental and mutant strains to several antimicrobials was assessed, as was the intracellular accumulation of the ethidium bromide dye. Regarding bacterial virulence, the role of these three efflux pumps on growth, strain fitness, motility, biofilm formation ability, survival in adverse conditions (oxidative stress and bile salts) and human serum and in vitro adhesion and invasion to Caco-2 cells was evaluated. We observed that the mutants from the three efflux pumps were more susceptible to several classes of antimicrobials than the parental strain and presented an increase in the accumulation of ethidium bromide, indicating a potential role of the efflux pumps in the extrusion of antimicrobials. The mutant strains had no bacterial growth defects; nonetheless, they presented a reduction in relative fitness. For the three mutants, an increase in the susceptibility to oxidative stress was observed, while only the mutant for AreGHI efflux pump showed a relevant role in bile stress survival. All the mutant strains showed an impairment in biofilm formation ability, were more susceptible to human serum and were less adherent to intestinal epithelial cells. Overall, the results support the contribution of the efflux pumps AreABC, AreDEF and AreGHI of A. butzleri to antimicrobial resistance, as well as to bacterial virulence.

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Tocopherols and Tocotrienols—Bioactive Dietary Compounds; What Is Certain, What Is Doubt?

International Journal of Molecular Sciences ◽

10.3390/ijms22126222 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6222

Author(s):

Kacper Szewczyk ◽

Aleksandra Chojnacka ◽

Magdalena Górnicka

Keyword(s):

Vitamin E ◽

Metabolic Disorders ◽

Tissue Concentration ◽

Biological Properties ◽

Biological Role ◽

Future Research ◽

The Past ◽

The Subject ◽

The Relationship

Tocopherols and tocotrienols are natural compounds of plant origin, available in the nature. They are supplied in various amounts in a diet, mainly from vegetable oils, some oilseeds, and nuts. The main forms in the diet are α- and γ-tocopherol, due to the highest content in food products. Nevertheless, α-tocopherol is the main form of vitamin E with the highest tissue concentration. The α- forms of both tocopherols and tocotrienols are considered as the most metabolically active. Currently, research results indicate also a greater antioxidant potential of tocotrienols than tocopherols. Moreover, the biological role of vitamin E metabolites have received increasing interest. The aim of this review is to update the knowledge of tocopherol and tocotrienol bioactivity, with a particular focus on their bioavailability, distribution, and metabolism determinants in humans. Almost one hundred years after the start of research on α-tocopherol, its biological properties are still under investigation. For several decades, researchers’ interest in the biological importance of other forms of vitamin E has also been growing. Some of the functions, for instance the antioxidant functions of α- and γ-tocopherols, have been confirmed in humans, while others, such as the relationship with metabolic disorders, are still under investigation. Some studies, which analyzed the biological role and mechanisms of tocopherols and tocotrienols over the past few years described new and even unexpected cellular and molecular properties that will be the subject of future research.

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