Potential Biocontrol Research Articles

The Biological Characteristics of Mycobacterium Phage Henu3 and the Fitness Cost Associated with Its Resistant Strains.

Tuberculosis (TB), caused by Mycobacterium tuberculosis, is an infectious disease that seriously affects human life and health. Despite centuries of efforts to control it, in recent years, the emergence of multidrug-resistant bacterial pathogens of M. tuberculosis due to various factors has exacerbated the disease, posing a serious threat to global health. Therefore, a new method to control M. tuberculosis is urgently needed. Phages, viruses that specifically infect bacteria, have emerged as potential biocontrol agents for bacterial pathogens due to their host specificity. In this study, a mycobacterium phage, Henu3, was isolated from soil around a hospital. The particle morphology, biological characteristics, genomics and phylogeny of Henu3 were characterized. Additionally, to explore the balance between phage resistance and stress response, phage Henu3-resistant strains 0G10 and 2E1 were screened by sequence passage and bidirectional validation methods, which significantly improved the sensitivity of phage to antibiotics (cefotaxime and kanamycin). By whole-genome re-sequencing of strains 0G10 and 2E1, 12 genes involved in cell-wall synthesis, transporter-encoded genes, two-component regulatory proteins and transcriptional regulatory factor-encoded genes were found to have mutations. These results suggest that phage Henu3 has the potential to control M. tuberculosis pathogens, and phage Henu3 has the potential to be a new potential solution for the treatment of M. tuberculosis infection.

Plant growth-promoting rhizobacteria enhance active ingredient accumulation in medicinal plants at elevated CO2 and are associated with indigenous microbiome.

Plant growth-promoting rhizobacteria (PGPR) and elevated CO2 (eCO2) have demonstrated their individual potential to enhance plant yield and quality through close interaction with rhizosphere microorganisms and plant growth. However, the efficacy of PGPR under eCO2 on rhizosphere microbiome and, ultimately, plant yield and active ingredient accumulation are not yet fully understood. This study investigated how the medicinal plant Pseudostellaria heterophylla (P. heterophylla) and its rhizosphere microbes respond to PGPR (Bacillus subtilis and Pseudomonas fluorescens) at eCO2 (1,000 ppm). It was found that the yield and active ingredient polysaccharides accumulation in the tuber of P. heterophylla were significantly increased by 38 and 253%, respectively. This promotion has been associated with increased root development and changes in the indigenous microbial community. Metagenomics analysis revealed a significant reduction in pathogenic Fusarium abundance in the rhizosphere. Potential biocontrol bacteria Actinobacteria and Proteobacteria were enriched, especially the genera Bradyrhizobium and Rhodanobacter. The reshaping of the rhizosphere microbiome was accompanied by the upregulation of biological pathways related to metabolite biosynthesis in the rhizosphere. These modifications were related to the promotion of the growth and productivity of P. heterophylla. Our findings highlighted the significant role played by PGPR in medicinal plant yield and active ingredient accumulation when exposed to eCO2.

Genomic insights and biocontrol potential of ten bacterial strains from the tomato core microbiome.

Despite their adverse environmental effects, modern agriculture relies heavily on agrochemicals to manage diseases and pests and enhance plant growth and productivity. Some of these functions could instead be fulfilled by endophytes from the plant microbiota, which have diverse activities beneficial for plant growth and health. We therefore used a microbiome-guided top-down approach to select ten bacterial strains from different taxa in the core microbiome of tomato plants in the production chain for evaluation as potential bioinoculants. High-quality genomes for each strain were obtained using Oxford Nanopore long-read and Illumina short-read sequencing, enabling the dissection of their genetic makeup to identify phyto-beneficial traits. Bacterial strains included both taxa commonly used as biofertilizers and biocontrol agents (i.e. Pseudomonas and Bacillus) as well as the less studied genera Leclercia, Chryseobacterium, Glutamicibacter, and Paenarthorbacter. When inoculated in the tomato rhizosphere, these strains promoted plant growth and reduced the severity of Fusarium Crown and Root Rot and Bacterial Spot infections. Genome analysis yielded a comprehensive inventory of genes from each strain related to processes including colonization, biofertilization, phytohormones, and plant signaling. Traits directly relevant to fertilization including phosphate solubilization and acquisition of nitrogen and iron were also identified. Moreover, the strains carried several functional genes putatively involved in abiotic stress alleviation and biotic stress management, traits that indirectly foster plant health and growth. This study employs a top-down approach to identify new plant growth-promoting rhizobacteria (PGPRs), offering an alternative to the conventional bottom-up strategy. This method goes beyond the traditional screening of the strains and thus can expand the range of potential bioinoculants available for market application, paving the way to the use of new still underexplored genera.

Isolation and characterization of two novel phages, ?Rspv1 and ?Rspv2, with a potential for biocontrol of Ralstonia solanacearum.

Bacteriophages offer an effective biocontrol strategy, presenting an environmentally friendly alternative to combat the issues of antibiotic and copper-based bactericide resistance in bacterial phytopathogens. In this study, two phages targeting Ralstonia solanacearun (designated as ?Rspv1 and ?Rspv2) were identified as potential biocontrol agents against solanaceous wilt, a highly destructive disease causing significant economic losses globally. Both phages demonstrated resistance to chloroform, while ?Rspv1 exhibited a broader host range compared to ?Rspv2 across five isolates of R. solanaceraum. The replication cycle for ?Rspv2 was determined to be 90 min. for a single growth cycle, with a burst size of 85 PFU per cell. Morphologically, ?Rspv1 featured icosahedral heads with long tails, characteristic of the Myoviridae family, whereas ?Rspv2 displayed a filamentous particle shape typical of Inoviridae viruses. Additionally, a Random Amplified Polymorphic DNA (RAPD) analysis using four random primers revealed a diverse nature of the two phages, suggesting their potential utility in disease management strategies. This research unveils two novel virulent phages, and their characterization highlights promising for phage therapy with future investigations aim to field level evaluation against R. solanacearum.

Mechanisms of action and biocontrol potential of Trichoderma against Fusarium in horticultural crops

Mechanisms of action and biocontrol potential of <i>Trichoderma</i> against <i>Fusarium</i> in horticultural crops

The growth-blocking peptide is a dual regulator of development and immunity with biocontrol potential in Spodoptera frugiperda (Lepidoptera: Noctuidae)

Insect growth-blocking peptides (GBPs) are a family of cytokines found in several insect orders and are known for their roles in regulating development, paralysis, cell proliferation, and immune responses. Despite their diverse functions, the potential of GBPs as biocontrol targets against the pest Spodoptera frugiperda (Lepidoptera: Noctuidae) has not been fully explored. In this study, S. frugiperda GBP (SfGBP) was identified and functionally characterized. SfGBP is synthesized as a 146 amino acid proprotein with a 24 amino acid C-terminal active peptide (Glu123-Gly146). Predominant expression of SfGBP occurs in fourth to sixth instar larvae and in the larval fat body, with significant upregulation in response to pathogens and pathogen-associated molecular patterns. Injection of the synthetic active peptide into larvae induced growth retardation, delayed pupation, and increased survival against Beauveria bassiana infection. Conversely, RNA interference-mediated knockdown of SfGBP resulted in accelerated growth, earlier pupation, and decreased survival against B. bassiana infection. Further analysis revealed that SfGBP promoted SF9 cell proliferation and spreading, enhanced bacteriostatic activity of larval hemolymph, and directly inhibited germination of B. bassiana conidia. In addition, SfGBP enhanced humoral responses, such as upregulation of immunity-related genes and generation of reactive oxygen species, and cellular responses, such as nodulation, phagocytosis, and encapsulation. These results highlight the dual regulatory role of SfGBP in development and immune responses and establish it as a promising biocontrol target for the management of S. frugiperda.

Antarctic Streptomyces: Promising biocontrol agents for combating Fusarium oxysporum f. sp. cubense

Fusarium wilt of Banana (FWB) caused by Fusarium oxysporum f. sp. cubense (Foc) poses a significant threat to the banana industry, with current inadequate control measures. This study evaluated the antifungal potential of nine Streptomyces strains isolated from Antarctic soil samples, using Casein-Starch media to stimulate the production of antifungal compounds. The inhibition spectrum against Foc was assessed under laboratory conditions using the well diffusion on Mueller-Hinton agar, with antifungal activity measured in arbitrary units (AU/mL) and minimum inhibitory concentration (MIC) tested using ethyl acetate extracts. Among the nine isolates, K6 and E7 were closely related to Streptomyces polyrhachis and Streptomyces fildesensis, exhibited significant antifungal activity, with K6 and E7 showing 320 and 80 AU/mL, and MIC values of 250 and >500 ppm, respectively. These findings highlight K6 and E7 as potential biocontrol agents against Foc, offering new avenues for sustainable Fusarium wilt management in banana cultivation.

Unveiling the multifaceted potential of Pseudomonas khavaziana strain SR9: a promising biocontrol agent for wheat crown rot.

Fusarium pseudograminearum, a soil-borne fungus, is the cause of the devastating wheat disease known as wheat crown rot (WCR). The persistence of this pathogen in the soil and crop residues contributes to the increased occurrence and severity of WCR. Therefore, developing effective strategies to prevent and manage WCR is of great importance. In this study, we isolated a bacterial strain, designated as SR9, from the stem of wheat, that exhibited potent antagonistic effects against F. pseudograminearum, as well as the biocontrol efficacy of SR9 on WCR was quantified at 83.99% ± 0.11%. We identified SR9 as Pseudomonas khavaziana and demonstrated its potential as a plant probiotic. SR9 displayed broad-spectrum antagonism against other fungal pathogens, including Neurospora dictyophora, Botrytis californica, and Botryosphaeria dothidea. Whole-genome sequencing analysis revealed that SR9 harbored genes encoding various cell wall-degrading enzymes, cellulases, and lipases, along with antifungal metabolites, which are responsible for its antagonistic activity. Gene knockout and quantitative PCR analyses reveal that phenazine is the essential factor for antagonism. SR9 possessed genes related to auxin synthesis, flagellar biosynthesis, biofilm adhesion, and the chemotaxis system, which play pivotal roles in plant colonization and growth promotion; we also evaluated the effects of SR9 on plant growth in wheat and Arabidopsis. Our findings strongly suggest that SR9 holds great promise as a biocontrol agent for WCR in sustainable agriculture.IMPORTANCEThe escalating prevalence of wheat crown rot, primarily attributed to Fusarium pseudograminearum, necessitates the development of cost-effective and eco-friendly biocontrol strategies. While plant endophytes are recognized for their biocontrol potential, reports on effective strains targeting wheat crown rot are sparse. This study introduces the Pseudomonas khavaziana SR9 strain as an efficacious antagonist to the wheat crown rot pathogen Fusarium pseudograminearum. Demonstrating a significant reduction in wheat crown rot incidence and notable plant growth promotion, SR9 emerges as a key contributor to plant health and agricultural sustainability. Our study outlines a biological approach to tackle wheat crown rot, establishing a groundwork for innovative sustainable agricultural practices.

Transcriptomic and metabolomic analyses provide evidence on the biocontrol mechanism responsible for the inhibition of Botrytis cinerea and Alternaria alternata by Bacillus velezensis in kiwifruit

AbstractBotrytis cinerea and Alternaria alternata are major pre‐ and postharvest plant pathogens of kiwifruit and responsible for significant economic losses. Although synthetic fungicides are the main source of controlling these pathogens, their use can lead to pathogen resistance, pollution of the environment, and their residues on agricultural produce can represent a health risk to humans. Bacillus velezensis is an ecofriendly bacterium with biocontrol potential. The objectives of the present study were to determine the efficacy of B. velezensis against B. cinerea and A. alternata, both of which are pre‐ and postharvest pathogens of kiwifruit, and investigate the mechanisms responsible for its biocontrol activity using transcriptomic and metabolomic methodology. Dual cultures of B. velezensis and either B. cinerea or A. alternata versus single cultures were used to conduct a transcriptomic and metabolomic analyses to provide insight into the mechanism by which B. velezensis inhibits B. cinerea and A. alternata. A total of 2499 and 3248 differentially expressed genes (DEGs) were identified in the B. velezensis/B. cinerea and B. velezensis/A. alternata comparisons, respectively. Genes related to sporulation, virulence, and hydrolase activity were downregulated in B. cinerea and A. alternata. Genes associated with MAPK signaling and the TCA cycle were also downregulated. Our study provides new insights into mechanism underlying the inhibition of B. cinerea and A. alternata by B. velezensis. Our results also demonstrate the potential of B. velezensis as a biocontrol agent against these two major pathogens of kiwifruit.

Phylogenetic systematics and integrative taxonomy contribute to weed biological control

Taxonomy and systematics are at the base of any biological research, providing the scientific names and evolutionary context to access the biological information needed. The biological control of weeds (BCW), like many other fields, often suffers from the “taxonomic impediment” generated by incomplete taxonomic knowledge or lack of available taxonomic experts on the particular taxa involved (i.e., weed plants and their potential biocontrol agents). Further, most groups with described species require revision by specialists using modern taxonomic methods. Systematists in the different taxonomic groups have the knowledge and experience to perform the accurate identification of the species involved in the study, to recognize if they are non-native species, or if they are new to science. Their expertise is crucial for identifying the organisms involved in BCW, including hybrids or cryptic species. The practice of phylogenetic systematics allows the discovery of evolutionary relationships and natural taxa that are valuable in making host range predictions. This contribution emphasizes the crucial role played by phylogenetic systematics and integrative taxonomy in weed biological control.

Aflatoxin B1 Control by Various Pseudomonas Isolates.

The climate-change-coupled fungal burden in crop management and the need to reduce chemical pesticide usage highlight the importance of finding sustainable ways to control Aspergillus flavus. This study examines the effectiveness of 50 Pseudomonas isolates obtained from corn rhizospheres against A. flavus in both solid and liquid co-cultures. The presence and quantity of aflatoxin B1 (AFB1) and AFB1-related compounds were determined using high-performance liquid chromatography-high resolution mass spectrometry analysis. Various enzymatic- or non-enzymatic mechanisms are proposed to interpret the decrease in AFB1 production, accompanied by the accumulation of biosynthetic intermediates (11-hydroxy-O-methylsterigmatocystin, aspertoxin, 11-hydroxyaspertoxin) or degradation products (the compounds C16H10O6, C16H14O5, C18H16O7, and C19H16O8). Our finding implies the upregulation or enhanced activity of fungal oxidoreductases and laccases in response to bacterial bioactive compound(s). Furthermore, non-enzymatic reactions resulted in the formation of additional degradation products due to acid accumulation in the fermented broth. Three isolates completely inhibited AFB1 or any AFB1-related compounds without significantly affecting fungal growth. These bacterial isolates supposedly block the entire pathway for AFB1 production in the fungus during interaction. Apart from identifying effective Pseudomonas isolates as potential biocontrol agents, this work lays the foundation for exploring new bacterial bioactive compounds.

Isolation and characterization of duck sewage source Salmonella phage P6 and antibacterial activity for recombinant endolysin LysP6

Salmonella is a globally prevalent foodborne pathogen, and adverse events caused by S. Enteritidis and S. Typhimurium are extremely common. With the emergence of drug resistance, there is an urgent need for efficient and specific lytic bacteriophages as alternative to antibiotics in clinical practice. In this study, phage P6 was isolated and screened from effluent and fecal samples from duck farm environments to specifically lyse the duck sources S. Typhimurium and S. Enteritidis. Phage P6 belongs to the genus Lederbergvirus, unclassified Lederbergvirus species. The phage P6 genome did not contained non-coding RNA, virulence genes and drug resistance genes, indicating that phage P6 was biologically safe for clinical applications. Phage P6 lysed 77.78% (28/36) of multidrug-resistant Salmonella and reduced biofilms formed by S. Enteritidis CVCC 3377, 4, and 24, and S. Typhimurium 44 by 44% to 75% within 3 h, and decreased Salmonella in duckling feces by up to 1.64 orders of magnitude. Prokaryotic expression of endolysin LysP6 lysed the chloroform-treated bacterial outer membrane from different serotypes of duck-derived Salmonella and E. coli standard strain ATCC 25922. The host range was expanded compared to phage P6, and the growth of Salmonella was effectively inhibited by LysP6 in conjunction with the membrane permeabilizer EDTA within 24 h. Therefore, phage P6 and phage-derived endolysins LysP6 are suitable for application as potent biocontrol agents to improve poultry health and food safety.

Bacillus velezensis Y6, a Potential and Efficient Biocontrol Agent in Control of Rice Sheath Blight Caused by Rhizoctonia solani.

Rice sheath blight is a serious disease caused by Rhizoctonia solani that reduces rice yield. Currently, there is a lack of efficient and environmentally friendly control methods. In this study, we found that Bacillus velezensis (B. velezensis) Y6 could significantly inhibit the growth of mycelium in Rhizoctonia solani, and its control efficiency against rice sheath blight was 58.67% (p < 0.01) in a pot experiment. Lipopeptides play an important role in the control of rice sheath blight by B. velezensis Y6, among which iturin and fengycin are essential, and iturin W, a novel lipopeptide in B. velezensis, plays a major role in lipopeptide antagonism to Rhizoctonia solani. In the field, we also found that inoculation with B. velezensis Y6 can increase rice yield (dry weight) by 11.75%. Furthermore, the transcriptome profiling results of the rice roots revealed that there were a total of 1227 differential genes (DEGs) regulated when treated with Y6, of which 468 genes were up-regulated and 971 genes were down-regulated in rice roots compared with the control. Among them, the DEGs were mainly distributed in biological processes (BP) and were mainly enriched in response to stimulus (GO:0050896), response to stress (GO:0006950), and response to abiotic stimulus (GO:0009628). According to the KEGG pathway analysis, there were 338 DEGs classified into 87 KEGG functional pathway categories. Compared with the control, a large number of enriched genes were distributed in phenylpropanoid biosynthesis (map00940), glutathione metabolism (map00480), glycolysis/gluconeogenesis (map00010), and amino sugar and nucleotide sugar metabolism (map00520). In summary, this investigation provides a new perspective for studying the molecular mechanism of B. velezensis in controlling rice sheath blight.

Biocontrol potential of Bacillus velezensis QF-2 isolated from rhizosphere soil of Vickifunkia tianschanica

Plant diseases caused by pathogenic fungi result in substantial losses of human, material, and financial resources annually. The common practice of chemical control often leads to the development of drug resistance in target organisms and carries adverse environmental impacts. As an alternative, researchers are exploring the potential of microbial control agents found in the rhizosphere.Previous studies have identified numerous promising microbial strains that could be utilized as effective, ecologically-friendly, and sustainable solutions to manage plant diseases. In the present investigation, a bacterial strain designated QF-2 was isolated from the rhizosphere soil of Vickifunkia tianschanica. Through dual culture experiments and molecular biological analysis, the taxonomic status of this strain was clearly established, and its antagonistic activities against seven plant pathogens were observed. Furthermore, the researchers conducted a comprehensive analysis of the QF-2 genome. Concurrently, five secondary metabolites (1–5) produced by QF-2 were studied, isolated, and identified.

Isolation of Antagonistic Endophytic Fungi from Postharvest Chestnuts and Their Biocontrol on Host Fungal Pathogens.

In this study, antagonistic endophytic fungi were isolated from postharvest chestnut fruits; endophytic antagonistic fungi and their combination of inhibitory effects on the fungal pathogen Neofusicoccum parvum were evaluated. A total of 612 endophytic fungi were isolated from 300 healthy chestnut kernels, and 6 strains out of them including NS-3, NS-11, NS-38, NS-43, NS-56, and NS-58 were confirmed as antagonistic endophytic fungi against Neofusicoccum parvum; these were separately identified as Penicillium chermesinum, Penicillium italicum, Penicillium decaturense, Penicillium oxalicum, Talarmyces siamensis, and Penicillium guanacastense. Some mixed antagonistic endophytic fungi, such as NS-3-38, NS-11-38, NS-43-56, and NS-56-58-38, exhibited a much stronger antifungal activity against N. parvum than that applied individually. Among them, the mixture of NS-3-38 showed the highest antifungal activity, and the inhibition rate was up to 86.67%. The fermentation broth of NS-3, NS-38, and their combinations exhibited an obvious antifungal activity against N. parvum, and the ethyl acetate phase extract of NS-3-38 had the strongest antifungal activity, for which the inhibitory rate was up to 90.19%. The NS-3-38 fermentation broth combined with a chitosan coating significantly reduced N. parvum incidence in chestnuts from 100% to 19%. Furthermore, the fruit decay and weight loss of chestnuts during storage were significantly decreased by the NS-3-38 fermentation broth mixture along with a chitosan coating. Therefore, a mixture of P. chermesinum and P. decaturense could be used as a potential complex biocontrol agent to control postharvest fruit decay in chestnuts.

Exploring the efficacy of endophytic Diaporthe caatingaensis as a biocontrol agent targeting Fusarium strains afflicting coffee plants in Saudi Arabia

BackgroundThe coffee plant is a strategic crop in Saudi Arabia that makes a substantial contribution to the country’s economy. Therefore, it is crucial to continuously monitor and control the fungal phytopathogens that affect coffee plants in order to minimize crop losses and ensure sustainable cultivation. This is the first surveillance report of Fusarium phytopathogens associated with coffee plants in Saudi Arabia. Moreover, the antagonistic efficiency of the endophytic fungus, Diaporthe caatingaensis, was evaluated against the isolated Fusarium phytopathogens. MethodsThe isolated strains were preliminary identified using cultural and microscopic methods and the identification was confirmed using internal transcribed spacer (ITS) sequencing technique. The detached leaf assay was conducted to assess the disease severity of Fusarium phytopathogens against detached coffee leaves. Moreover, dual culture assay was utilized to assess the antagonistic activity of D. caatingaensis. Results and conclusionFusarium oxysporum was found to be the most frequent isolated strain followed by F. solani, F. proliferatum and F. verticillioides strains. Fusarium proliferatum strain was found to be the most severe strain whereas F. solani strain showed the lowest disease severity. On the other hand, propiconazole fungicide was tested for its efficiency against Fusarium pathogens using food poisoning technique, showing that F. oxysporum strain 1 of accession number OP955665 was the most sensitive strain. However, F. proliferatum, F. oxysporum st. 2 (OP959851) and F. solani strains showed no significant response when the propiconazole concentration increase from 150 to 200 ppm. Scanning electron microscope proved the potent antagonistic activity of D. caatingaensis against F. proliferatum and F. oxysporum OP959874 strains through mycoparasitic modes of action as coiling, appressorium formation resulting in complete lysis of fungal mycelium. Accordingly, the current investigation provides the first surveillance data about Fusarium strains associated with coffee plants and also the utilization of D. caatingaensis as a potential biocontrol agent for effective management of Fusarium phytopathogens, avoiding the incidence of fungal resistance to fungicides and the harmful effects of commercial fungicides for sustainable cultivation of coffee in Saudi Arabia.

Pseudomonas and Acinetobacter spp. capable of metabolizing aromatics displays multifarious plant growth promoting traits: Insights on strategizing consortium-based application to agro-ecosystems

The persistence and slow rate of natural attenuation of genotoxic and endocrine-disrupting aromatic pollutants has impacted the soil heath of agro-ecologies leading to various health and environmental issues. Ecotoxic-xenobiotic compounds degradation property along with plant growth promoting traits of microbes are beneficial for devising strategies for improved agricultural soil health and its clean-up. Present study assessed the multipartite plant growth promoting-, biocontrol- and niche adaptive- traits of five aromatic degrading soil bacteria viz. Pseudomonas bharatica CSV86T, Pseudomonas sp. C5pp, Pseudomonas sp. PP4, Pseudomonas sp. PPD and Acinetobacter sp. ISP4. Solubilization of rock phosphate (P) and feldspar (K), production of plant growth hormone (auxin; IAA), ammonia, siderophores and ACC deaminase by strain CSV86T, C5pp and PP4 were observed. Similarly, high fusaric acid resistance (MIC: 1–1.2 mg mL−1) and tolerance to salinity (5–7.5 %) was observed. In vitro application of CSV86T, C5pp, PP4 and ISP4 as consortium resulted in significant increase (P < 0.05) in the seedling shoot length (15–37 %), root length (65–150 %) and biomass (30–40 %) of wheat, mung bean and fenugreek. In-soil microcosm assay confirmed the plant growth promoting and phytoprotective ability of this consortium against toxicity of aromatics in contaminated soil. Antifungal activity against phytopathogenic fungi Magnaporthe oryzae and Aspergillus spp., ability to produce lytic enzymes and HCN suggests their biocontrol potential. Four aromatic degrading bacteria (as a consortium) exhibiting plant growth promotion and biocontrol activity could be used as an eco-friendly bioremediator-biofertilizer-biocontrol agent (bioformulation) for restoration of agricultural soil with improved crop productivity.

Reproductive Biology and Rearing Improvements of Apanteles opuntiarum, Potential Biocontrol Agent of the Argentine Cactus Moth, Cactoblastis cactorum.

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae) is native to South America and has been used as a biocontrol agent of Opuntia (Cactaceae) in Australia and South Africa. Its invasion in North America has raised concerns for the native Opuntia in the USA and Mexico. We investigated the reproductive biology and rearing procedures of a host-specific potential biocontrol agent, Apanteles opuntiarum Martínez and Berta (Hymenoptera: Braconidae). Given the gregarious nature of the parasitoid larvae, we studied the morphology of the immature stages and evaluated evidence of polyembryony and superparasitism. We also investigated the effects of host exposure arena and host density on parasitism rates and wasp production. The morphological descriptions provide a basis for comparison with other species. Early larval instars of A. opuntiarum are similar to other microgastrine immature stages. However, the mature larva exhibits placoid sensilla in the epistomal region, a unique character not previously reported. We provide evidence that A. opuntiarum eggs are not polyembryonic; females frequently superparasitize and have an oviposition preference for larvae parasitized 1-2 d previously. Exposing larvae of C. cactorum to wasps while inside the cactus resulted in lower parasitism and fewer offspring from each host than exposing larvae in the arena without the cactus. Parasitism and mortality rates were higher at lower host densities, possibly due to reduced host group defensive behavior. These results suggest that preference for superparasitism, host defensive behavior, and interactions with the cactus may play an important role in per-host wasp production under laboratory conditions.

Characterization and application of LysSGF2 and HolSGF2 as potential biocontrol agents against planktonic and biofilm cells of common pathogenic bacteria

Antimicrobial resistance represents a global health emergency, necessitating the introduction of novel antimicrobial agents. In the present study, lysozyme and holin from Shigella flexneri 1.1868 phage SGF2, named LysSGF2 and HolSGF2, respectively, were cloned, expressed, and characterized. LysSGF2 and HolSGF2 showed lytic activities against S. flexneri 1.1868 cells at 4–55 °C and pH 3.1–10.3. LysSGF2 exhibited antimicrobial activity against five gram-negative and two gram-positive bacteria. HolSGF2 showed antimicrobial activity against four gram-negative and one gram-positive species. The antibacterial activities of LysSGF2 and HolSGF2 were determined in liquid beverages, including bottled water and milk. The relative lytic activity of LysSGF2 combined with HolSGF2 against the tested bacteria was approximately 46–77 % in water. Furthermore, the combination markedly decreased the viable counts of tested bacteria by approximately 3–5 log CFU/mL. LysSGF2 and HolSGF2 could efficiently remove biofilms on polystyrene, glass, and stainless-steel. The efficacy of the LysSGF2 and HolSGF2 combination against the tested bacteria on polystyrene was 58–71 %. Combination treatment effectively killed biofilm cells formed on stainless-steel and glass by 1–4 log CFU/mL. ese results indicate that LysSGF2 and HolSGF2 can successfully control both the planktonic and biofilm cells of common pathogenic bacteria, suggesting that the combined or single use of LysSGF2 and HolSGF2 may be of great value in food processing.

Stenotrophomonas maltophilia G17: Potential antifungal agent isolated from the gut of black soldier fly larvae against Ganoderma boninense

Oil palm (Elaeis guineensis Jacq.) is the primary source of foreign exchange in Indonesia's plantation sector. However, these plants are very vulnerable to attack by Ganoderma spp., which causes basal stem rot (BSR) and upper stem rot (USR) disease, resulting in significant economic losses. In this study, antagonistic assays of the G17 isolate obtained from the gut of black soldier fly (BSF) larvae showed potential biocontrol against G. boninense. Furthermore, antibiosis assays showed that the Stenotrophomonas maltophilia G17 isolate inhibited the growth of G. boninense by up to 85.56%–91.98%. Molecular identification using 16S rRNA, reinforced by biochemical characterization tests, confirmed the G17 isolate as S. maltophilia. Growth test results showed that S. maltophilia G17 cannot grow at a temperature of 37 °C within 24 h. The isolate also exhibited negative hemolytic activity, indicating it is not a pathogenic bacterium. S. maltophilia G17 exhibited lytic enzymes such as proteolytic, lipolytic, and chitinolytic activity. Among them, chitinolytic enzymes might be involved in the biocontrol process.