Biological Control Of Bacterial Diseases Research Articles

Characterisation of New Foxunavirus Phage Murka with the Potential of Xanthomonas campestris pv. campestris Control.

Phages of phytopathogenic bacteria are considered to be promising agents for the biological control of bacterial diseases in plants. This paper reports on the isolation and characterisation of a new Xanthomonas campestris pv. campestris phage, Murka. Phage morphology and basic kinetic characteristics of the infection were determined, and a phylogenomic analysis was performed. The phage was able to lyse a reasonably broad range (64%, 9 of the 14 of the Xanthomonas campestris pv. campestris strains used in the study) of circulating strains of the cabbage black rot pathogen. This lytic myovirus has a DNA genome of 44,044 bp and contains 83 predicted genes. Taxonomically, it belongs to the genus Foxunavirus. This bacteriophage is promising for use as a possible means of biological control of cabbage black rot.

Inhibitive and prophylactic efficacy of lactic acid bacteria from Apis mellifera (Hymenoptera: Apidae) in combating Paenibacillus infections

Given the increasing interest in alternative methods of prevention and biological control of bacterial diseases in honey bees, the development of new approaches based on probiotic bacteria for honey bee growth, immune function and defense is important. Honey bees have a rich microbiota that varies with seasonal and geographic changes, developmental stages, diet, and social lifestyle. Nevertheless, lactic acid bacteria are an integral part of the honey bee microbiota. In this study, strains of Apilactobacillus, Leuconostoc and Enterococcus isolated from healthy honey bees were identified and their usefulness as an alternative product to control and prevent American and European foulbrood was investigated. The strains were identified by cultural and molecular analysis. The antimicrobial activities against Paenibacillus larvae and Paenibacillus alvei were tested by agar plug and well diffusion method. The inhibitory effect of the obtained 72-h cell-free supernatants on Paenibacillus larvae spore germination was determined by the Bioscreen C method. It turned out that the strains whose prophylactic effect against Paenibacillus larvae spores in larvae was tested were not largely able to prevent infection. Apilactobacillus and Leuconostoc strains did not affect the health of the larvae, and infection was somewhat clinically eliminated in larvae colonized by Apilactobacillus and Enterococcus. The fact that the strains exhibit potent antimicrobial activity and do not reduce larval viability and live weight is a promising finding with regard to their use for treatment, particularly in the early stages of American foulbrood infection.

Isolation, characterization, and evaluation of putative new bacteriophages for controlling bacterial spot on tomato in Brazil.

Bacterial spot is a highly damaging tomato disease caused by members of several species of the genus Xanthomonas. Bacteriophages have been studied for their potential use in the biological control of bacterial diseases. In the current study, bacteriophages were obtained from soil and tomato leaves in commercial fields in Brazil with the aim of obtaining biological control agents against bacterial spot. Phage isolation was carried out by co-cultivation with isolates of Xanthomonas euvesicatoria pv. perforans, which was prevalent in the collection areas. In a host range evaluation, none of the phage isolates was able to induce a lytic cycle in all of the bacterial isolates tested. In in vivo tests, treatment of susceptible bacterial isolates with the corresponding phage prior to application to tomato plants led to a reduction in the severity of the resulting disease. The level of disease control provided by phage application was equal to or greater than that achieved using copper hydroxide. Electron microscopy analysis showed that all of the phages had similar morphology, with head and tail structures similar to those of viruses belonging to the class Caudoviricetes. The presence of short, non-contractile tubular tails strongly suggested that these phages belong to the family Autographiviridae. This was confirmed by phylogenetic analysis, which further revealed that they all belong to the genus Pradovirus. The phages described here are closely related to each other and potentially belong to a new species within the genus. These phages will be evaluated in future studies against other tomato xanthomonad strains to assess their potential as biological control agents.

Antibacterial Activity of Different Strains of the Genus Trichoderma

The main pathogens causing plant diseases are bacteria, viruses, and fungi. A number of strategies are usually used for plant protection and control of pathogenic microorganisms. The main interest of researchers is focused on the development of alternative synthetic chemicals to control bacterial diseases of plants. Among such approaches, biological control of bacterial diseases using agents such as antagonistic fungi and some other microorganisms is considered to be one of the most effective strategies. Species of the genus Trichoderma are known for their antagonistic activity against plant pathogenic fungi and bacteria and can be an effective safety strategy to control them. An important peculiarity of fungi of this genus is their ability to inhibit target pathogenic organisms without harming non-target (beneficial) microorganisms. The study of the antagonistic activity of fungi of the genus Trichoderma was conducted mainly against pathogenic fungi of agricultural plants. At the same time, the study of the antibacterial activity of fungi of this genus has attracted much less attention. Therefore, the aim of our work was to determine the antibacterial activity of microscopic fungi of the genus Trichoderma against test cultures of bacteria causing pathogenesis of agricultural plants. Methods. The objects of research were 100 fungal strains of the genus Trichoderma and six economically important plant pathogenic bacteria such as Pseudomonas syringae UCM В-1027Т, Pseudomonas fluorescens 8573, Pectobacterium carotovorum UCM В-1095T, Xanthomonas campestris pv. campestris UCM В-1049, Clavibacter michiganensis subsp. michiganensis 102, and Agrobacterium tumefaciens UCM В-1000. Cultures of the studied fungi were grown on potato-dextrose agar. The antagonistic activity of fungi of the genus Trichoderma against plant pathogenic bacteria was studied using the conventional method of diffusion in agar and method of dual culture. The antibacterial activity of culture filtrates of Trichoderma strains was evaluated via the zone of growth inhibition of plant pathogenic bacteria. The percentages of growth inhibition of plant pathogenic bacteria were calculated, and the antagonistic activity of strains was concluded on the basis of the obtained values. Results. In general, the studied Trichoderma strains had the antagonistic activity against plant pathogenic bacteria. Using method of diffusion in agar, it was shown that among the 100 studied Trichoderma strains, 12 had the effect of growth inhibition (bacteriostatic effect) of all six studied species of pathogenic bacteria; 20 strains inhibited the growth of five ones, 36 — four, 12 — three, and 7 — of two strains. The strains with a wide spectrum of antibacterial activity were studied by the double culture method. This made it possible to demonstrate the high selectivity of the antagonistic effect of Trichoderma strains on individual test cultures of phytopathogenic bacteria. For example, strain No7A inhibited the growth of C. michiganensis subsp. michiganensis 102 by 47% and the growth of P. syringae UCM B-1027T by 30%, while the zones of growth inhibition of these test cultures, determined by the method of diffusion in agar, were 5 and 6 mm, respectively. Conclusions. The obtained results indicated the potential and overall ability of Trichoderma strains to biologically control bacterial pathogens. The most promising for the use of plant pathogenic bacteria as agents for biocontrol were strains F-60, 1515, and 320, which were active against all studied bacteria. Such strains may have the potential as a preventive biocontrol agent of plant pathogens with a wide range of action. On the other hand, Trichoderma strains with high activity against certain pathogens may have the potential to be used as a control agent against a specific target pathogen.

Study on Antibacterial and Quorum-Sensing Inhibition Activities of Cinnamomum camphora Leaf Essential Oil.

Many essential oils (EOs) regulate the quorum-sensing (QS) system of pathogens and inhibit the virulence expression. Interference with QS can potentially reduce bacterial multidrug resistance and aid the biological control of bacterial disease. In the present work, the antibacterial and anti-QS activities of Cinnamomum camphora leaf EO were investigated. A total of 23 chemical components with relative levels ≥0.11%, including a large number of terpene compounds, were identified in C. camphora leaf EO by gas chromatography–mass spectrometry (GC-MS). The principal component was linalool, followed by eucalyptol, with relative levels of 51.57% and 22.07%, respectively. The minimum inhibitory concentration (MIC) and antibacterial activity of C. camphora EO were examined, and P. aeruginosa and E. coli ATCC25922 showed the highest and lowest sensitivity to C. camphora EO, respectively. Tests of QS inhibitory activity revealed that C. camphora EO significantly decreased the production of violacein and biofilm biomass in C. violaceum, with the maximum inhibition rates of 63% and 77.64%, respectively, and inhibited the biofilm formation and swarming movement, independent of affecting the growth of C. violaceum. Addition of C. camphora EO also resulted in downregulation of the expression of the acyl-homoserine lactones (AHL) synthesis gene (cviI) and transcription regulator (cviR), and inhibited the expression of QS-regulated virulence genes, including vioA, vioB, vioC, vioD, vioE, lasA, lasB, pilE3, and hmsHNFR. Collectively, the prominent antibacterial activity and anti-QS activities clearly support that C. camphora EO acts as a potential antibacterial agent and QS inhibitor in the prevention of bacterial contamination.

Microparticles containing gallic and ellagic acids for the biological control of bacterial diseases of kiwifruit plants

Over the last decades, kiwifruit cultivation has gained increasing importance all over the world, but some bacterial diseases seriously threaten its cultivation. The most dangerous one is the bacterial canker caused by Pseudomonas syringae pv. actinidiae Takikawa et al., but also floral bud necrosis by Pseudomonas syringae pv. syringae van Hall and bacterial blight by Pseudomonas viridiflava (Burkholder) Dowson affect kiwifruit plants. Their control relies mainly on antibiotics, where allowed, and copper, although this adversely affects the environment, so that alternative control measures are needed. Here we investigate gallic acid and ellagic acid, substances easily obtainable from some plant tissues, for their antimicrobial activity aiming to use them as support in the biocontrol of kiwifruit bacterial diseases. These active principles demonstrated their effectiveness as pure substances in both in vitro and in vivo tests. Moreover, their encapsulation in methacrylate polymeric microparticles showed to improve their usefulness and to prolong remarkably their activity up to 14 days after the treatment, when applied in greenhouse or in field on artificially and naturally infected plants, respectively. The encouraging results obtained by this type of microformulation point the way to future alternative biological control strategies against kiwifruit bacterial diseases.

Efeito "in vitro" de antibióticos e rizobactérias no controle de bactérias fitopatogênicas ao Eucalyptus spp.

Doenças causadas por bactérias constituem um novo desafio à cultura do Eucalyptus spp., podendo, inclusive, limitar o uso de clones suscetíveis. O presente trabalho objetivou avaliar a eficiência de antibióticos e rizobactérias na inibição do crescimento "in vitro" de isolados de bactérias fitopatogênicas ao Eucalyptus spp. na fase de viveiro e de campo. O antibiótico sulfato de amicacina e a rizobactéria S1 (Bacillus subtillis) destacaram-se quanto à inibição do crescimento do isolado fitopatogênico IP1-05 (Pseudomonas chichorii), enquanto a cefoxitina causou maior inibição dos isolados BSV16 e RVV11 (Rhizobium sp.). Os antibióticos de uso comercial na área agronômica, Mycoshield (oxitetraciclina) e Agrimicina (estreptomicina e tetraciclina) foram pouco efetivos. Este trabalho proporciona embasamento a alternativas para controle biológico de doenças bacterianas em mudas de Eucalyptus spp. na fase de viveiro.