A Model and Image Based Investigation of X. fastidiosa Within Host Dynamics

Photosynthesis relies on the transport of water and sugars from roots to leaves facilitated by two key tissues: xylem and phloem. Blockages in the xylem/phloem, either by structures formed by the pathogen itself or those formed by the plant as a defence mechanism, disrupt the soil-plant-atmosphere continuum and cause many vascular plant disease symptoms. Xylella fastidiosa (X. fastidiosa) is a bacterium that colonises internal plant vascular networks causing pathogenic effects on several commercially important crops, including those associated with the olive quick decline syndrome causing devastating olive decline in Apulia, Southern Italy. Despite a growing research effort since the recent detection of X. fastidiosa in Europe, the exact processes leading to X. fastidiosa disease symptoms are not fully understood due to difficulties in observing internal plant structures. Our goal is to utilise models to elucidate fundamental processes that lead to olive quick decline syndrome. We are developing a mathematical model describing within-host biofilm development that predicts water-stresses that ultimately inhibit plant functionality. Our approach is centred on the assumption that the biofilm structure is determined by the arrangement of extracellular polysaccharide (EPS) molecules, and as such, our model contains a polymer-physical description of X. fastidiosa biofilm formation dynamics. We used our model, requiring minimal empirical assumptions, to replicate biofilm aggregation observed by microfluidics. We have also produced X-ray Computed Tomography (XCT) images of vascular networks in both resistant and susceptible olive cultivars. We are using these images to test whether susceptibility is correlated with morphological differences that might influence fluid flow through the plant. This work improves the understanding of possible cultivar resistance mechanisms to aid informed breeding and orchard management, and model simulations will provide insights for understanding xylem blockages and their relation to observed symptom severity.

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Hidden Host Plant Associations of Soilborne Fungal Pathogens: An Ecological Perspective

Phytopathology ◽

10.1094/phyto-08-12-0192-le ◽

2013 ◽

Vol 103 (6) ◽

pp. 538-544 ◽

Cited By ~ 86

Author(s):

Glenna M. Malcolm ◽

Gretchen A. Kuldau ◽

Beth K. Gugino ◽

María del Mar Jiménez-Gasco

Keyword(s):

Host Plant ◽

Population Biology ◽

Fungal Pathogens ◽

Current Knowledge ◽

Vascular Plant ◽

Disease Symptoms ◽

Nonhost Plant ◽

Plant Associations ◽

Definition Of ◽

Forest Plants

Much of the current knowledge on population biology and ecology of soilborne fungal pathogens has been derived from research based on populations recovered from plants displaying disease symptoms or soil associated with symptomatic plants. Many soilborne fungal pathogens are known to cause disease on a large number of crop plants, including a variety of important agronomical, horticultural, ornamental, and forest plants species. For instance, the fungus Verticillium dahliae causes disease on >400 host plants. From a phytopathological perspective, plants on which disease symptoms have not been yet observed are considered to be nonhosts for V. dahliae. This term may be misleading because it does not provide information regarding the nature of the plant–fungus association; that is, a nonhost plant may harbor the fungus as an endophyte. Yet, there are numerous instances in the literature where V. dahliae has been isolated from asymptomatic plants; thus, these plants should be considered hosts. In this article, we synthesize scattered research that indicates that V. dahliae, aside from being a successful and significant vascular plant pathogen, may have a cryptic biology on numerous asymptomatic plants as an endophyte. Thus, we suggest here that these endophytic associations among V. dahliae and asymptomatic plants are not unusual relationships in nature. We propose to embrace the broader ecology of many fungi by differentiating between “symptomatic hosts” as those plants in which the infection and colonization by a fungus results in disease, and “asymptomatic hosts” as those plants that harbor the fungus endophytically and are different than true nonhosts that should be used for plant species that do not interact with the given fungus. In fact, if we broaden our definition of “host plant” to include asymptomatic plants that harbor the fungus as an endophyte, it is likely that the host ranges for some soilborne fungal pathogens are much larger than previously envisioned. By ignoring the potential for soilborne fungal pathogens to display endophytic relationships, we leave gaps in our knowledge about the population biology and ecology, persistence, and spread of these fungi in agroecosystems.

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The Xylella fastidiosa-Resistant Olive Cultivar “Leccino” Has Stable Endophytic Microbiota during the Olive Quick Decline Syndrome (OQDS)

Pathogens ◽

10.3390/pathogens9010035 ◽

2019 ◽

Vol 9 (1) ◽

pp. 35 ◽

Cited By ~ 7

Author(s):

Marzia Vergine ◽

Joana B. Meyer ◽

Massimiliano Cardinale ◽

Erika Sabella ◽

Martin Hartmann ◽

...

Keyword(s):

Xylella Fastidiosa ◽

Resistance Mechanisms ◽

16S Rrna Genes ◽

Rrna Genes ◽

Olive Cultivar ◽

Olive Quick Decline Syndrome ◽

Olive Trees ◽

Potential Interactions ◽

Highly Virulent

Xylella fastidiosa is a highly virulent pathogen that causes Olive Quick Decline Syndrome (OQDS), which is currently devastating olive plantations in the Salento region (Apulia, Southern Italy). We explored the microbiome associated with X. fastidiosa-infected (Xf-infected) and -uninfected (Xf-uninfected) olive trees in Salento, to assess the level of dysbiosis and to get first insights into the potential role of microbial endophytes in protecting the host from the disease. The resistant cultivar “Leccino” was compared to the susceptible cultivar “Cellina di Nardò”, in order to identify microbial taxa and parameters potentially involved in resistance mechanisms. Metabarcoding of 16S rRNA genes and fungal ITS2 was used to characterize both total and endophytic microbiota in olive branches and leaves. “Cellina di Nardò” showed a drastic dysbiosis after X. fastidiosa infection, while “Leccino” (both infected and uninfected) maintained a similar microbiota. The genus Pseudomonas dominated all “Leccino” and Xf-uninfected “Cellina di Nardò” trees, whereas Ammoniphilus prevailed in Xf-infected “Cellina di Nardò”. Diversity of microbiota in Xf-uninfected “Leccino” was higher than in Xf-uninfected “Cellina di Nardò”. Several bacterial taxa specifically associated with “Leccino” showed potential interactions with X. fastidiosa. The maintenance of a healthy microbiota with higher diversity and the presence of cultivar-specific microbes might support the resistance of “Leccino” to X. fastidiosa. Such beneficial bacteria might be isolated in the future for biological treatment of the OQDS.

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Cryptococcus neoformans Biofilm Formation Depends on Surface Support and Carbon Source and Reduces Fungal Cell Susceptibility to Heat, Cold, and UV Light

Applied and Environmental Microbiology ◽

10.1128/aem.02506-06 ◽

2007 ◽

Vol 73 (14) ◽

pp. 4592-4601 ◽

Cited By ~ 102

Author(s):

Luis R. Martinez ◽

Arturo Casadevall

Keyword(s):

Cryptococcus Neoformans ◽

Biofilm Formation ◽

Capsular Polysaccharide ◽

Uv Light ◽

Surface Characteristics ◽

Extracellular Polysaccharide ◽

Microtiter Plate ◽

Support Surface ◽

Fungal Cell ◽

Biofilm Development

ABSTRACT The fungus Cryptococcus neoformans possesses a polysaccharide capsule and can form biofilms on medical devices. We describe the characteristics of C. neoformans biofilm development using a microtiter plate model, microscopic examinations, and a colorimetric 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino) carbonyl]-2H-tetrazolium-hydroxide (XTT) reduction assay to observe the metabolic activity of cryptococci within a biofilm. A strong correlation between XTT and CFU assays was demonstrated. Chemical analysis of the exopolymeric material revealed sugar composition consisting predominantly of xylose, mannose, and glucose, indicating the presence of other polysaccharides in addition to glucurunoxylomannan. Biofilm formation was affected by surface support differences, conditioning films on the surface, characteristics of the medium, and properties of the microbial cell. A specific antibody to the capsular polysaccharide of this fungus was used to stain the extracellular polysaccharide matrix of the fungal biofilms using light and confocal microscopy. Additionally, the susceptibility of C. neoformans biofilms and planktonic cells to environmental stress was investigated using XTT reduction and CFU assays. Biofilms were less susceptible to heat, cold, and UV light exposition than their planktonic counterparts. Our findings demonstrate that fungal biofilm formation is dependent on support surface characteristics and that growth in the biofilm state makes fungal cells less susceptible to potential environmental stresses.

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Antibiotic susceptibility of Staphylococcus aureus with different degrees of biofilm formation

Journal of Analytical Science & Technology ◽

10.1186/s40543-021-00294-2 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Hyo-Jung Shin ◽

Sungtae Yang ◽

Yong Lim

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Antimicrobial Agents ◽

Resistance Mechanisms ◽

Minimal Bactericidal Concentration ◽

Chronic Infections ◽

Planktonic Bacteria ◽

Growth Modes ◽

Biofilm Bacteria ◽

Biofilm Development

AbstractStaphylococcus aureus is one of the most common pathogens in biofilm-associated chronic infections. S. aureus living within biofilms evades the host immune response and is more resistant to antibiotics than planktonic bacteria. In this study, we generated S. aureus with low and high levels of biofilm formation using the rbf (regulator of biofilm formation) gene and performed a BioTimer assay to determine the minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of various types of antibiotics. We showed that biofilm formation by S. aureus had a greater effect on MBC than MIC, probably due to the different growth modes between planktonic and biofilm bacteria. Importantly, we found that the MBC for biofilm S. aureus was much higher than that for planktonic cells, but there was little difference in MBC between low and high levels of biofilm formation. These results suggest that once the biofilm is formed, the bactericidal activity of antibiotics is significantly reduced, regardless of the degree of S. aureus biofilm formation. We propose that S. aureus strains with varying degrees of biofilm formation may be useful for evaluating the anti-biofilm activity of antimicrobial agents and understanding antibiotic resistance mechanisms by biofilm development.

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Salmonella and the Immune System

10.5772/intechopen.95673 ◽

2021 ◽

Author(s):

Weam Saad Al-Hamadany

Keyword(s):

Immune Response ◽

Immune System ◽

Innate Immune Response ◽

Human Body ◽

Pathogenic Bacteria ◽

Adaptive Immune Response ◽

Resistance Mechanisms ◽

Personal Hygiene ◽

Disease Symptoms ◽

Adaptive Immune

The human body has many mechanisms to resist invaders like pathogenic bacteria to avoid harm according to the living creature’s law “survival for the best”. On the opposite; Salmonella as pathogenic bacteria have many weapons that they utilize to invade the human body. The resistance mechanisms expressed by the human body are called immunity which represented by the immune system that has many different types of resistance processes, either specific (adaptive immune response) or non-specific (Innate Immune Response) against certain pathogenic invaders. As far as these processes are strong they will be enough to avoid infections occurrence, otherwise, the human body will get infected with Salmonella, be ill, show the disease symptoms, transmit the disease to others, and may become a carrier for the pathogen according to many circumstances. Prevention is still stood the most effective way to avoid getting infected with Salmonella by personal hygiene or suitable vaccination if available.

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Ionomic Differences between Susceptible and Resistant Olive Cultivars Infected by Xylella fastidiosa in the Outbreak Area of Salento, Italy

Pathogens ◽

10.3390/pathogens8040272 ◽

2019 ◽

Vol 8 (4) ◽

pp. 272 ◽

Cited By ~ 10

Author(s):

Giusy D’Attoma ◽

Massimiliano Morelli ◽

Pasquale Saldarelli ◽

Maria Saponari ◽

Annalisa Giampetruzzi ◽

...

Keyword(s):

Inductively Coupled Plasma ◽

Xylella Fastidiosa ◽

Optical Emission ◽

Host Genotype ◽

Bacterial Populations ◽

Inductively Coupled ◽

Outbreak Area ◽

Olive Cultivars ◽

Olive Quick Decline Syndrome ◽

Olive Trees

Olive quick decline syndrome (OQDS) is a devastating disease of olive trees in the Salento region, Italy. This disease is caused by the bacterium Xylella fastidiosa, which is widespread in the outbreak area; however, the “Leccino” variety of olives has proven to be resistant with fewer symptoms and lower bacterial populations than the “Ogliarola salentina” variety. We completed an empirical study to determine the mineral and trace element contents (viz; ionome) of leaves from infected trees comparing the two varieties, to develop hypotheses related to the resistance of Leccino trees to X. fastidiosa infection. All samples from both cultivars tested were infected by X. fastidiosa, even if leaves were asymptomatic at the time of collection, due to the high disease pressure in the outbreak area and the long incubation period of this disease. Leaves were binned for the analysis by variety, field location, and infected symptomatic and infected asymptomatic status by visual inspection. The ionome of leaf samples was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES) and compared with each other. These analyses showed that Leccino variety consistently contained higher manganese (Mn) levels compared with Ogliarola salentina, and these levels were higher in both infected asymptomatic and infected symptomatic leaves. Infected asymptomatic and infected symptomatic leaves within a host genotype also showed differences in the ionome, particularly a higher concentration of calcium (Ca) and Mn levels in the Leccino cultivar, and sodium (Na) in both varieties. We hypothesize that the ionome differences in the two varieties contribute to protection against disease caused by X. fastidiosa infection.

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The rnc Gene Regulates the Microstructure of Exopolysaccharide in the Biofilm of Streptococcus mutans through the β-Monosaccharides

Caries Research ◽

10.1159/000518462 ◽

2021 ◽

Vol 55 (5) ◽

pp. 534-545

Author(s):

Yangyu Lu ◽

Hongyu Zhang ◽

Meng Li ◽

Mengying Mao ◽

Jiaqi Song ◽

...

Keyword(s):

Dental Caries ◽

Streptococcus Mutans ◽

Bacterial Adhesion ◽

Extracellular Polysaccharide ◽

Water Soluble ◽

Glycosidic Bond ◽

Glycosidic Bonds ◽

Overexpression Strain ◽

1H Nuclear Magnetic Resonance ◽

Biofilm Development

Streptococcus mutans is known as the crucial pathogen of human dental caries, owing to its contribution to the biofilm development via the capacity of synthesizing exopolysaccharide (EPS), which mainly compose of α-glycosidic bond and β-glycosidic bond. β-glycosidic bond is less flexible than α-glycosidic bond because of differences between their configurational properties. Previous studies have shown that the rnc gene is implicated in the EPS formation and the cariogenicity of S. mutans. However, the effects of rnc on the microstructure of EPS have been not well-understood yet. Here, we further investigated how the rnc gene worked to modulate microstructural properties of the extracellular polysaccharide of S. mutans using glycomics methods. The gas chromatography-mass spectrometer showed that the proportion of glucose was decreased in water-soluble EPS and galactose was absent in water-insoluble EPS from the S. mutans rnc-deficient strain (Smurnc), compared with the isogenic wild-type strain (UA159). The composition of functional groups and the displacement of hydrogen bond were analyzed by infrared radiation and 1H nuclear magnetic resonance, respectively. In addition, phenotypic modulation of the biofilm matrix was assessed by microscopy. We found that the EPS of UA159 and the rnc overexpression strain (Smurnc+) mainly consisted of β-glycosidic bonds. Conversely, the EPS of Smurnc were made up of mostly α-glycosidic bonds, leading to the attenuation of biofilm biomass and bacterial adhesion. Furthermore, the existence of β-glycosidic bond was verified by enzyme digestion. Collectively, the rnc gene modulates the conversion of β-glycosidic bonds, which may play important roles in regulating the micromolecule structure of the EPS matrix, thus affecting the characteristics of S. mutans biofilm. These data illustrate that β-glycosidic bonds mediated by rnc may be potential targets for the prevention and treatment of dental caries.

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Resistance of New Zealand Provenance Leptospermum scoparium, Kunzea robusta, Kunzea linearis, and Metrosideros excelsa to Austropuccinia psidii

Plant Disease ◽

10.1094/pdis-11-19-2302-re ◽

2020 ◽

Vol 104 (6) ◽

pp. 1771-1780 ◽

Cited By ~ 2

Author(s):

Grant R. Smith ◽

Beccy J. Ganley ◽

David Chagné ◽

Jayanthi Nadarajan ◽

Ranjith N. Pathirana ◽

...

Keyword(s):

New Zealand ◽

Resistance Mechanisms ◽

Rust Disease ◽

Disease Symptoms ◽

Stem Infection ◽

Stem Resistance ◽

New Finding ◽

Austropuccinia Psidii ◽

Assessment Scales ◽

Leptospermum Scoparium

Resistance to the pandemic strain of Austropuccinia psidii was identified in New Zealand provenance Leptospermum scoparium, Kunzea robusta, and K. linearis plants. Only 1 Metrosideros excelsa-resistant plant was found (of the 570 tested) and no resistant plants of either Lophomyrtus bullata or L. obcordata were found. Three types of resistance were identified in Leptospermum scoparium. The first two, a putative immune response and a hypersensitive response, are leaf resistance mechanisms found in other myrtaceous species while on the lateral and main stems a putative immune stem resistance was also observed. Both leaf and stem infection were found on K. robusta and K. linearis plants as well as branch tip dieback that developed on almost 50% of the plants. L. scoparium, K. robusta, and K. linearis are the first myrtaceous species where consistent infection of stems has been observed in artificial inoculation trials. This new finding and the first observation of significant branch tip dieback of plants of the two Kunzea spp. resulted in the development of two new myrtle rust disease severity assessment scales. Significant seed family and provenance effects were found in L. scoparium, K. robusta, and K. linearis: some families produced significantly more plants with leaf, stem, and (in Kunzea spp.) branch tip dieback resistance, and provenances provided different percentages of resistant families and plants. The distribution of the disease symptoms on plants from the same seed family, and between plants from different seed families, suggested that the leaf, stem, and branch tip dieback resistances were the result of independent disease resistance mechanisms.

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Elucidation of the Disease Cycle of Olive Anthracnose Caused by Colletotrichum acutatum

Phytopathology ◽

10.1094/phyto-99-5-0548 ◽

2009 ◽

Vol 99 (5) ◽

pp. 548-556 ◽

Cited By ~ 33

Author(s):

Juan Moral ◽

Rodrígues de Oliveira ◽

Antonio Trapero

Keyword(s):

Latent Infection ◽

Toxic Substance ◽

Fruit Rot ◽

Colletotrichum Acutatum ◽

Phenological Stages ◽

Disease Symptoms ◽

Immature Fruit ◽

Olive Cultivars ◽

Detached Leaves ◽

Branch Dieback

Anthracnose, caused by Colletotrichum acutatum and C. gloeosporioides, is a major fungal disease of olive in many countries. In Spain, the disease has been associated only with a characteristic rot and mummification of mature fruit. The purpose of this study was to determine whether C. acutatum could infect other plant tissues that may serve as sources of inoculum for anthracnose epidemics. Inoculations of young plants or detached leaves and field observations demonstrated that flowers and immature olive fruit are susceptible to the pathogen. Flower infection caused blight of inflorescences and infection of developing fruit. Immature fruit were infected in all phenological stages, although infection remained latent for 7 to 8 months, until the onset of fruit ripening. Fruit susceptibility increased and latent period decreased with maturity. Fruit were required for symptom development on inoculated plants. Plants without fruit were infected but they did not show any disease symptoms. Only plants with rotten fruit developed leaf wilting and branch dieback symptoms several weeks later. These results, together with the low level of pathogen isolation from affected leaves and branches and the toxicity of sterile fungal extracts to olive cuttings, suggest that a toxic substance produced by C. acutatum in rotten fruit may account for this syndrome. Both disease syndromes, fruit rot and branch dieback, developed in several olive cultivars, which were equally susceptible to the pathogen. However, olive cultivars differed in their response to flower and fruit infection. Latent infection of developing fruit during the spring may permit survival of the pathogen during the hot and dry summer and serve as an inoculum source for anthracnose epidemics that develop on ripening fruit in autumn.

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Complete Genome Sequence of the Olive-Infecting Strain Xylella fastidiosa subsp. pauca De Donno

Genome Announcements ◽

10.1128/genomea.00569-17 ◽

2017 ◽

Vol 5 (27) ◽

Cited By ~ 16

Author(s):

Annalisa Giampetruzzi ◽

Maria Saponari ◽

Rodrigo P. P. Almeida ◽

Salwa Essakhi ◽

Donato Boscia ◽

...

Keyword(s):

Genome Sequence ◽

Complete Genome Sequence ◽

Complete Genome ◽

Xylella Fastidiosa ◽

Olive Tree ◽

Pathogenic Bacterium ◽

Plant Pathogenic Bacterium ◽

Content Type ◽

Olive Cultivars ◽

Olive Quick Decline Syndrome

ABSTRACT We report here the complete and annotated genome sequence of the plant-pathogenic bacterium Xylella fastidiosa subsp. pauca strain De Donno. This strain was recovered from an olive tree severely affected by olive quick decline syndrome (OQDS), a devastating olive disease associated with X. fastidiosa infections in susceptible olive cultivars.

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