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14 pages, 4070 KiB

Open AccessArticle

A New Kayfunavirus-like Escherichia Phage vB_EcoP-Ro45lw with Antimicrobial Potential of Shiga Toxin-Producing Escherichia coli O45 Strain

by Xincheng Sun, Yen-Te Liao, Yujie Zhang, Alexandra Salvador, Kan-Ju Ho and Vivian C. H. Wu

Microorganisms 2023, 11(1), 77; https://doi.org/10.3390/microorganisms11010077 - 27 Dec 2022

Cited by 2 | Viewed by 3012

Abstract

Lytic bacteriophages are re-considered as a solution to resolve antibiotic-resistant rampage. Despite frequent foodborne outbreaks caused by the top six non-O157 Shiga-toxin-producing Escherichia coli (STEC), the current interventions are not sufficiently effective against each serogroup, particularly O45. Therefore, this study aimed to characterize [...] Read more.

Lytic bacteriophages are re-considered as a solution to resolve antibiotic-resistant rampage. Despite frequent foodborne outbreaks caused by the top six non-O157 Shiga-toxin-producing Escherichia coli (STEC), the current interventions are not sufficiently effective against each serogroup, particularly O45. Therefore, this study aimed to characterize a new short-tailed phage, vB_EcoP-Ro45lw (or Ro45lw), as an alternative antimicrobial agent for STEC O45 strains. Phage Ro45lw belongs to the Kayfunavirus genus within the Autographiviridae family and shares no close evolutionary relationship with any reference phages. Ro45lw contains a tail structure composed of a unique tail fiber and tail tubular proteins A and B, likely to produce enzymatic activity against the target bacterial cells besides structural function. Additionally, the phage genome does not contain virulent, antibiotic-resistant, or lysogenic genes. The phage has a latent period of 15 min with an estimated burst size of 55 PFU/CFU and is stable at a wide range of pH (pH4 to pH11) and temperatures (30 °C to 60 °C). Regardless of the MOIs (MOI = 0.1, 1, and 10) used, Ro45lw has a strong antimicrobial activity against both environmental (E. coli O45:H-) and clinical (E. coli O45:H2) strains at 25 °C. These findings indicate that phage Ro45lw has antimicrobial potential in mitigating pathogenic STEC O45 strains. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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26 pages, 5984 KiB

Open AccessArticle

Characterization and Assessment of 2, 4-Diacetylphloroglucinol (DAPG)-Producing Pseudomonas fluorescens VSMKU3054 for the Management of Tomato Bacterial Wilt Caused by Ralstonia solanacearum

by Perumal Suresh, Murukesan Rekha, Subramanian Gomathinayagam, Vellaisamy Ramamoorthy, Mahaveer P. Sharma, Perumal Sakthivel, Karuppannan Sekar, Mariadhas Valan Arasu and Vellasamy Shanmugaiah

Microorganisms 2022, 10(8), 1508; https://doi.org/10.3390/microorganisms10081508 - 26 Jul 2022

Cited by 15 | Viewed by 3172

Abstract

Microbial bio-products are becoming an appealing and viable alternative to chemical pesticides for effective management of crop diseases. These bio-products are known to have potential to minimize agrochemical applications without losing crop yield and also restore soil fertility and productivity. In this study, [...] Read more.

Microbial bio-products are becoming an appealing and viable alternative to chemical pesticides for effective management of crop diseases. These bio-products are known to have potential to minimize agrochemical applications without losing crop yield and also restore soil fertility and productivity. In this study, the inhibitory efficacy of 2,4-diacetylphloroglucinol (DAPG) produced by Pseudomonas fluorescens VSMKU3054 against Ralstonia solanacearum was assessed. Biochemical and functional characterization study revealed that P. fluorescens produced hydrogen cyanide (HCN), siderophore, indole acetic acid (IAA) and hydrolytic enzymes such as amylase, protease, cellulase and chitinase, and had the ability to solubilize phosphate. The presence of the key antimicrobial encoding gene in the biosynthesis of 2,4-diacetylphloroglucinol (DAPG) was identified by PCR. The maximum growth and antimicrobial activity of P. fluorescens was observed in king’s B medium at pH 7, 37 °C and 36 h of growth. Glucose and tryptone were found to be the most suitable carbon and nitrogen sources, respectively. DAPG was separated by silica column chromatography and identified by various methods such as UV-Vis, FT-IR, GC-MS and NMR spectroscopy. When R. solanacearum cells were exposed to DAPG at 90 µg/mL, the cell viability was decreased, reactive oxygen species (ROS) were increased and chromosomal DNA was damaged. Application of P. fluorescens and DAPG significantly reduced the bacterial wilt incidence. In addition, P. fluorescens was also found effective in promoting the growth of tomato seedlings. It is concluded that the indigenous isolate P. fluorescens VSMKU3054 could be used as a suitable biocontrol agent against bacterial wilt disease of tomato. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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18 pages, 4049 KiB

Open AccessArticle

Conidial Emulsion Formulation and Thermal Storability of Metarhizium anisopliae against Red Palm Weevil, Rhynchophorusferrugineus Olivier (Coleoptera: Dryophthoridae)

by Cheong Jia Lei, Najihah Abdul Halim, Norhayu Asib, Azlina Zakaria and Wahizatul Afzan Azmi

Microorganisms 2022, 10(7), 1460; https://doi.org/10.3390/microorganisms10071460 - 19 Jul 2022

Cited by 11 | Viewed by 3058

Abstract

Industrial crops including coconut palm and other palm species are seriously infested by red palm weevil (RPW), resulting in significant economic damage globally. Therefore, this study aimed to develop a mycoinsecticide utilizing conidia of Metarhizium anisopliae to control RPW and sought to investigate [...] Read more.

Industrial crops including coconut palm and other palm species are seriously infested by red palm weevil (RPW), resulting in significant economic damage globally. Therefore, this study aimed to develop a mycoinsecticide utilizing conidia of Metarhizium anisopliae to control RPW and sought to investigate a new emulsion formulation for the influences of storage temperature and heat stress on conidia germination in an oil-in-glycerol emulsion system. The mycoinsecticide is an emulsion formulation which comprises an oil carrier, non-ionic surfactants, water, and glycerol, which was optimized by premixing the oil and non-ionic surfactant in different weight ratios (1:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4: 6, 3: 7, 2:8, 1:9, and 0:1). From three selected oil-in-glycerol formulations, F25 was more stable in storage and had a smaller particle size (between 154.3 and 236.4 nm in diameter) and stable zeta potential (above + 30 mV) with low surface tension (29.83 ± 0.24 mN/m to 30.72 ± 0.11 mN/m at room temperature. Extended conidial viability was observed at 4 °C overall; the emulsion formulation maintained 12–15% conidial viability until the eighth week at room temperature. Heat of over 30 °C showed an inhibitory effect on conidial germination. This study revealed that the oil-in-glycerol formulation was stable and able to prolong conidial shelf life as compared to non-formulated conidia. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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17 pages, 3831 KiB

Open AccessArticle

The Microbiome of the ‘Williams’ Pear Variety Grown in the Organic Orchard and Antifungal Activity by the Autochthonous Bacterial and Yeast Isolates

by Tamara Janakiev, Tanja Berić, Tatjana Stević, Slaviša Stanković, Jasmina Bačić, Helena Majstorović, Djordje Fira and Ivica Dimkić

Microorganisms 2022, 10(7), 1282; https://doi.org/10.3390/microorganisms10071282 - 24 Jun 2022

Cited by 5 | Viewed by 2518

Abstract

The total diversity of bacterial and fungal communities associated with the phyllosphere (fruits and leaves) of the ‘Williams’ pear variety was analyzed in two phenological stages during fruit development and maturation. The antagonistic potential of autochthonous bacterial and yeast isolates against phytopathogenic fungi [...] Read more.

The total diversity of bacterial and fungal communities associated with the phyllosphere (fruits and leaves) of the ‘Williams’ pear variety was analyzed in two phenological stages during fruit development and maturation. The antagonistic potential of autochthonous bacterial and yeast isolates against phytopathogenic fungi was also evaluated. A metabarcoding approach revealed Pantoea, Sphingomonas, Hymenobacter, Massilia, and Pseudomonas as dominant bacterial constituents of the pear phyllosphere, whilst most abundant among the fungal representatives identified were Metschnikowia, Filobasidium, Aureobasidiumpullulans, Botrytis cinerea, and Taphrina. The traditional culturable approach revealed that the Pseudomonas genus with P. graminis, P. putida, and P. congelans was most prevalent. The most frequently cultivated fungal representatives belonged to the genus Fusarium with six identified species. A broad range of the antagonistic activity was detected for the Hannaella luteola and Metschnikowia pulcherrima yeasts, significantly affecting the growth of many fungal isolates in the range of 53–70%. Fusarium sporotrichioides was the most susceptible fungal isolate. The autochthonous antagonistic yeasts H. luteola and M. pulcherrima might be powerful biological control agents of postharvest diseases caused by Fusarium spp. and common pathogens like Monilinia laxa, Botrytis cinerea, Alternaria tenuissima, and Cladosporium cladosporioides. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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21 pages, 2312 KiB

Open AccessArticle

Root-Knot Disease Suppression in Eggplant Based on Three Growth Ages of Ganoderma lucidum

by Saba Fatima, Faryad Khan, Mohd Asif, Saqer S. Alotaibi, Khushbu Islam, Mohammad Shariq, Arshad Khan, Mohd Ikram, Faheem Ahmad, Tabreiz Ahmad Khan, Rampratap Meena and Mansoor Ahmad Siddiqui

Microorganisms 2022, 10(5), 1068; https://doi.org/10.3390/microorganisms10051068 - 23 May 2022

Cited by 5 | Viewed by 2545

Abstract

This investigation presents a novel finding showing the effect of culture filtrates (CFs) of macrofungi, Ganoderma lucidum, against Meloidogyne incognita evaluated in vitro and in planta. To determine the nematicidal activity, juveniles of M. incognita were exposed to Ganoderma CFs of three [...] Read more.

This investigation presents a novel finding showing the effect of culture filtrates (CFs) of macrofungi, Ganoderma lucidum, against Meloidogyne incognita evaluated in vitro and in planta. To determine the nematicidal activity, juveniles of M. incognita were exposed to Ganoderma CFs of three different ages (Two, four and eight weeks old) of pileus and stipe at different concentrations, i.e., 100%, 50%, 10% and 1% for different time intervals (12, 24, 48 and 72 h). Ganoderma species were examined morphologically based on external appearance and analytically using SEM. The ethanolic samples of basidiocarp were prepared and analyzed for in vitro nematicidal assay and different bioactive compounds. The in vitro experiment results revealed that among all three ages of pileus and stipe, two-week-old pileus and stipe exhibited great nematotoxic potency and caused 83.8% and 73.8% juveniles’ mortality at 100% concentration after 72 h of exposure time, respectively. Similarly, the two-week-old pileus and stipe showed the highest egg hatching inhibition of 89.2% and 81.0% at the 100% concentration after five days. The eight-week-old pileus and stipe were not more effective than the two- and four-week-old pileus and stipe. The metabolites were characterized using GC-MS, including sugar alcohol, steroids, silanes, glucosides, pyrones, ester, oleic acid, phthalic acid, linoleic acid, palmitates and ketones. The in planta study conducted in the greenhouse demonstrated that the root dip treatment for 30 min with Ganoderma CFs curtailed the infection level of M. incognita and promoted the eggplant plant growth. The maximum percent increase in plant length, plant fresh weight, plant dry weight, total chlorophyll, carotenoids and yield/plant was obtained at 100% conc. of fungus CFs, whereas a reduction was observed in nematode infestation parameters. It was concluded from the study that Ganoderma CFs can be explored as an effective and eco-friendly antinemic biocontrol agent in fields infected with root-knot nematodes. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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11 pages, 2532 KiB

Open AccessArticle

Biosurfactant-Producing Bacillus velezensis PW192 as an Anti-Fungal Biocontrol Agent against Colletotrichum gloeosporioides and Colletotrichum musae

by Watthanachai Jumpathong, Bungonsiri Intra, Jirayut Euanorasetr and Pagakrong Wanapaisan

Microorganisms 2022, 10(5), 1017; https://doi.org/10.3390/microorganisms10051017 - 12 May 2022

Cited by 17 | Viewed by 3061

Abstract

In this study, plant-root-associated Bacillus species were evaluated as antifungal biocontrol agents by analyzing the production of surface bioactive molecules known as lipopeptide biosurfactants. This study aimed to isolate and characterize antifungal biosurfactant-producing Bacillus bacterium. Bacillusvelezensis PW192 was isolated from the rhizosphere [...] Read more.

In this study, plant-root-associated Bacillus species were evaluated as antifungal biocontrol agents by analyzing the production of surface bioactive molecules known as lipopeptide biosurfactants. This study aimed to isolate and characterize antifungal biosurfactant-producing Bacillus bacterium. Bacillusvelezensis PW192 was isolated from the rhizosphere of Lagerstroemia macrocarpa var macrocarpa and identified based on phylogenetic analysis of the 16S rRNA gene. The biosurfactant was excreted to cultured supernatant and exhibited emulsification power up to 60% and a decrease in surface tension from 72 in distilled water to 21 mN/m. The surface tension properties were stable in a broad range of pH from 6 to 10, in high temperatures up to 100 °C, and in salinities with a NaCl concentration up to 12% (w/v). Starting from 0.5 mg of acid, precipitated crude biosurfactant exhibited antifungal activity toward Anthracnose, caused by the phytopathogens Colletotrichum gloeosporioides and C. musae. The chemical structures of the biosurfactant were structurally characterized as lipopeptides fengycin A and fengycin B. The stability of the biosurfactant, as well as the antifungal properties of B. velezensis PW192, can potentially make them useful as agricultural biocontrol agents, as well as in other biotechnological applications. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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17 pages, 5461 KiB

Open AccessArticle

Effects of ε-Poly-L-Lysine Combined with Wuyiencin as a Bio-Fungicide against Botryris cinerea

by Zhaoyang Lv, Yanxuan Lu, Boya Li, Liming Shi, Kecheng Zhang and Beibei Ge

Microorganisms 2022, 10(5), 971; https://doi.org/10.3390/microorganisms10050971 - 5 May 2022

Cited by 7 | Viewed by 2459

Abstract

This study mainly evaluated the broad-spectrum fungicidal activity of ε-poly L lysine (ε-PL) against 12 pathogenic fungi. We further demonstrated synergistic antifungal activity of ε-PL combined with wuyiencin against Botryris cinerea. The combined bio-fungicide achieved an inhibition rate of 100% for mycelial [...] Read more.

This study mainly evaluated the broad-spectrum fungicidal activity of ε-poly L lysine (ε-PL) against 12 pathogenic fungi. We further demonstrated synergistic antifungal activity of ε-PL combined with wuyiencin against Botryris cinerea. The combined bio-fungicide achieved an inhibition rate of 100% for mycelial growth using ε-PL at 500 μg/mL + wuyiencin at 50 μg/mL and for spore germination using ε-PL at 200 μg/mL + wuyiencin at 80 μg/mL in vitro. This synergistic spore and mycelia-damaging effect of the combination was confirmed using scanning electron microscopy. In vivo assays with combined bio-fungicide (1500 μg/mL ε-PL + 60 μg/mL wuyiencin) on detached leaves showed depressed growth and development of the spores of B. cinerea. The synergistic effect was further tested in combinations of ε-PL with wuyiencin by measuring the fractional inhibition concentration index (FICI) value below 0.5. Moreover, ε-PL and wuyiencin inoculation before B. cinerea infection significantly increased the superoxide dismutase, peroxidase, catalase, and phenylalanine ammonia-lyase activities, which suggested their involvement in tomato defense responses to disease to minimize damage to B. cinerea. These findings revealed that a combined bio-fungicide comprising ε-PL and wuyiencin had a good prospect for controlling plant fungal disease. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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15 pages, 1156 KiB

Open AccessArticle

Streptomyces sp. AN090126 as a Biocontrol Agent against Bacterial and Fungal Plant Diseases

by Khanh Duy Le, Nan Hee Yu, Ae Ran Park, Dong-Jin Park, Chang-Jin Kim and Jin-Cheol Kim

Microorganisms 2022, 10(4), 791; https://doi.org/10.3390/microorganisms10040791 - 8 Apr 2022

Cited by 45 | Viewed by 5369

Abstract

Bacteria and fungi are major phytopathogens which substantially affect global agricultural productivity. In the present study, Streptomyces sp. AN090126, isolated from agricultural suppressive soil in Korea, showed broad-spectrum antagonistic activity against various phytopathogenic bacteria and fungi. In the 96-well plate assay, the fermentation [...] Read more.

Bacteria and fungi are major phytopathogens which substantially affect global agricultural productivity. In the present study, Streptomyces sp. AN090126, isolated from agricultural suppressive soil in Korea, showed broad-spectrum antagonistic activity against various phytopathogenic bacteria and fungi. In the 96-well plate assay, the fermentation filtrate of Streptomyces sp. AN090126 exhibited antimicrobial activity, with a minimum inhibitory concentration (MIC) of 0.63–10% for bacteria and 0.63–3.3% for fungi. The MIC of the partially purified fraction was 20.82–250 µg/mL for bacteria and 15.6–83.33 µg/mL for fungi. Gas chromatography–mass spectrometry (GC-MS) analysis revealed that AN090126 produced various volatile organic compounds (VOCs), including dimethyl sulfide and trimethyl sulfide, which inhibited the growth of pathogenic bacteria and fungi in in vitro VOC assays. In pot experiments, the fermentation broth of Streptomyces sp. AN090126 reduced tomato bacterial wilt caused by Ralstonia solanacearum, red pepper leaf spot caused by Xanthomonas euvesicatoria, and creeping bentgrass dollar spot caused by Sclerotinia homoeocarpa in a dose-dependent manner. Moreover, the secondary metabolites derived from this strain showed a synergistic effect with streptomycin sulfate against streptomycin-resistant Pectobacterium carotovorum subsp. carotovorum, the causative agent of Kimchi cabbage soft rot, in both in vitro and in vivo experiments. Therefore, Streptomyces sp. AN090126 is a potential biocontrol agent in controlling plant diseases caused by pathogenic bacteria and fungi, specifically by the streptomycin-resistant strains. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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18 pages, 10450 KiB

Open AccessArticle

Suppressive Effect of Bioactive Extracts of Bacillus sp. H8-1 and Bacillus sp. K203 on Tomato Wilt Caused by Clavibacter michiganensis subsp. michiganensis

by Hwajin Jang, Sang Tae Kim and Mee Kyung Sang

Microorganisms 2022, 10(2), 403; https://doi.org/10.3390/microorganisms10020403 - 9 Feb 2022

Cited by 8 | Viewed by 2516

Abstract

Tomatoes are cultivated worldwide, and are economically important. Clavibacter michiganensis subsp. michiganensis (Cmm) is a pathogen that causes canker and wilting in tomatoes, resulting in serious damage to tomato plants. We aimed to control Cmm proliferation using substances produced by useful [...] Read more.

Tomatoes are cultivated worldwide, and are economically important. Clavibacter michiganensis subsp. michiganensis (Cmm) is a pathogen that causes canker and wilting in tomatoes, resulting in serious damage to tomato plants. We aimed to control Cmm proliferation using substances produced by useful microorganisms. The water extracts of strains H8-1 and K203 inhibited wilting caused by Cmm and slowed the pathogenic colonization in tomato plants. The relative expressions of celA, celB, pat1, and pelA of Cmm treated with the bacterial water extracts were reduced by 0.41-, 0.01-, 0.15-, and 0.14-fold for H8-1, respectively, and 0.45-, 0.02-, 0.13-, and 0.13-fold for K203, respectively, compared to controls at 72 h after treatments. In tomato plants inoculated with Cmm, when water extracts of H8-1 and K203 were treated, relative expression of ACO encoding 1-aminocyclopropane-1-carboxylic acid oxidase was suppressed by 0.26- and 0.23-fold, respectively, while PR1a was increased by 1.94- and 2.94-fold, respectively; PI2 expression was increased by 3.27-fold in water extract of H8-1-treated plants. As antioxidant enzymes of plants inoculated with Cmm, peroxidase and glutathione peroxidase levels were increased in K203-water-extract-treated plants, and catalase was increased in the case of the H8-1 water extract at 10 days after inoculation. In terms of soil enzyme activity, each water extract tended to increase urease activity and microbial diversity; in addition, K203 water extract increased plant growth. Thus, H8-1 and K203 water extracts can be used as potential biocontrol agents against Cmm. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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Review

Jump to: Research

16 pages, 1953 KiB

Open AccessReview

Roles of Arbuscular mycorrhizal Fungi as a Biocontrol Agent in the Control of Plant Diseases

by Wenfeng Weng, Jun Yan, Meiliang Zhou, Xin Yao, Aning Gao, Chao Ma, Jianping Cheng and Jingjun Ruan

Microorganisms 2022, 10(7), 1266; https://doi.org/10.3390/microorganisms10071266 - 22 Jun 2022

Cited by 72 | Viewed by 8752

Abstract

Arbuscularmycorrhizal fungi (AMF) are a class of beneficial microorganisms that are widely distributed in soil ecosystems and can form symbionts with 80% of terrestrial higher plants, and improve the nutritional status of plants. The use of AMF as a biocontrol method to [...] Read more.

Arbuscularmycorrhizal fungi (AMF) are a class of beneficial microorganisms that are widely distributed in soil ecosystems and can form symbionts with 80% of terrestrial higher plants, and improve the nutritional status of plants. The use of AMF as a biocontrol method to antagonize soil-borne pathogens has received increasing interest from phytopathologists and ecologists. In this paper, the mechanisms of resistance to diseases induced by AMF and the application of AMF to plant fungal, bacterial, and nematode diseases have been summarized. This study aimed to enhance the potential use of AMF as a biological control method to prevent plant diseases in the future. Root morphological alteration characteristics were explained, including the influence of AMF on root structure, function, and the regulation of AMF via secondary metabolites. AMF can improve the rhizosphere environment by influencing the physical and chemical proprieties of soil, enhancing the growth of other beneficial microorganisms, and by competing with pathogenic microorganisms. Two microorganism types may compete for the same invasive sites in root systems and regulate nutrition distribution. AMF can induce the host plant to form defense systems, including improving phytohormone concentrations, inducing signal substrate production, gene expression regulation, and enhancing protein production. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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18 pages, 844 KiB

Open AccessReview

Combining Desirable Traits for a Good Biocontrol Strategy against Sclerotinia sclerotiorum

by Daphné Albert, Tim Dumonceaux, Odile Carisse, Carole Beaulieu and Martin Filion

Microorganisms 2022, 10(6), 1189; https://doi.org/10.3390/microorganisms10061189 - 9 Jun 2022

Cited by 14 | Viewed by 4297

Abstract

The fungal pathogen Sclerotinia sclerotiorum (Helotiales: Sclerotiniaceae) causes white mold, a disease that leads to substantial losses on a wide variety of hosts throughout the world. This economically important fungus affects yield and seed quality, and its control mostly relies on the use [...] Read more.

The fungal pathogen Sclerotinia sclerotiorum (Helotiales: Sclerotiniaceae) causes white mold, a disease that leads to substantial losses on a wide variety of hosts throughout the world. This economically important fungus affects yield and seed quality, and its control mostly relies on the use of environmentally damaging fungicides. This review aimed to present the latest discoveries on microorganisms and the biocontrol mechanisms used against white mold. A special focus is put on the identification of biocontrol desirable traits required for efficient disease control. A better understanding of the mechanisms involved and the conditions required for their action is also essential to ensure a successful implementation of biocontrol under commercial field conditions. In this review, a brief introduction on the pathogen, its disease cycle, and its main pathogenicity factors is presented, followed by a thorough description of the microorganisms that have so far demonstrated biocontrol potential against white mold and the mechanisms they use to achieve control. Antibiosis, induced systemic resistance, mycoparasitism, and hypovirulence are discussed. Finally, based on our actual knowledge, the best control strategies against S. sclerotiorum that are likely to succeed commercially are discussed, including combining biocontrol desirable traits of particular interest. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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25 pages, 1029 KiB

Open AccessReview

Root-Associated Bacteria Are Biocontrol Agents for Multiple Plant Pests

by Jang Hoon Lee, Anne J. Anderson and Young Cheol Kim

Microorganisms 2022, 10(5), 1053; https://doi.org/10.3390/microorganisms10051053 - 19 May 2022

Cited by 13 | Viewed by 3704

Abstract

Biological control is an important process for sustainable plant production, and this trait is found in many plant-associated microbes. This study reviews microbes that could be formulated into pesticides active against various microbial plant pathogens as well as damaging insects or nematodes. The [...] Read more.

Biological control is an important process for sustainable plant production, and this trait is found in many plant-associated microbes. This study reviews microbes that could be formulated into pesticides active against various microbial plant pathogens as well as damaging insects or nematodes. The focus is on the beneficial microbes that colonize the rhizosphere where, through various mechanisms, they promote healthy plant growth. Although these microbes have adapted to cohabit root tissues without causing disease, they are pathogenic to plant pathogens, including microbes, insects, and nematodes. The cocktail of metabolites released from the beneficial strains inhibits the growth of certain bacterial and fungal plant pathogens and participates in insect and nematode toxicity. There is a reinforcement of plant health through the systemic induction of defenses against pathogen attack and abiotic stress in the plant; metabolites in the beneficial microbial cocktail function in triggering the plant defenses. The review discusses a wide range of metabolites involved in plant protection through biocontrol in the rhizosphere. The focus is on the beneficial firmicutes and pseudomonads, because of the extensive studies with these isolates. The review evaluates how culture conditions can be optimized to provide formulations containing the preformed active metabolites for rapid control, with or without viable microbial cells as plant inocula, to boost plant productivity in field situations. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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25 pages, 1665 KiB

Open AccessReview

Biological Control of Acinetobacter baumannii: In Vitro and In Vivo Activity, Limitations, and Combination Therapies

by Benjamin Havenga, Brandon Reyneke, Monique Waso-Reyneke, Thando Ndlovu, Sehaam Khan and Wesaal Khan

Microorganisms 2022, 10(5), 1052; https://doi.org/10.3390/microorganisms10051052 - 19 May 2022

Cited by 7 | Viewed by 3202

Abstract

The survival, proliferation, and epidemic spread of Acinetobacter baumannii (A. baumannii) in hospital settings is associated with several characteristics, including resistance to many commercially available antibiotics as well as the expression of multiple virulence mechanisms. This severely limits therapeutic options, with [...] Read more.

The survival, proliferation, and epidemic spread of Acinetobacter baumannii (A. baumannii) in hospital settings is associated with several characteristics, including resistance to many commercially available antibiotics as well as the expression of multiple virulence mechanisms. This severely limits therapeutic options, with increased mortality and morbidity rates recorded worldwide. The World Health Organisation, thus, recognises A. baumannii as one of the critical pathogens that need to be prioritised for the development of new antibiotics or treatment. The current review will thus provide a brief overview of the antibiotic resistance and virulence mechanisms associated with A. baumannii’s “persist and resist strategy”. Thereafter, the potential of biological control agents including secondary metabolites such as biosurfactants [lipopeptides (surfactin and serrawettin) and glycolipids (rhamnolipid)] as well as predatory bacteria (Bdellovibrio bacteriovorus) and bacteriophages to directly target A. baumannii, will be discussed in terms of their in vitro and in vivo activity. In addition, limitations and corresponding mitigations strategies will be outlined, including curtailing resistance development using combination therapies, product stabilisation, and large-scale (up-scaling) production. Full article

(This article belongs to the Special Issue Microorganisms as Biocontrol Agents)

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