Endophytic Bacterial Isolates Research Articles

Chitinase Enzyme-Producing Endophytic Bacterias From the Roots of the Plant Gembolo (Dioscorea bulbifera): Isolation, Characterization and its Potential as an Antifungal Agent

Chitinase is an enzyme of the chitinolytic group that has many roles in agriculture, especially as an antifungal, because chitin is one of the constituent components of the fungal cell wall. This study aimed to isolate and identify endophytic bacteria from gembolo (Dioscorea bulbifera) roots and to characterize the chitinase enzyme from these endophytic bacteria to be used as an antifungal. Isolation and identification of gembolo plant root endophytic bacteria using PCR method of 16S rRNA gene amplification and sequencing. Characterization of the chitinase enzyme produced includes determining of optimum pH, temperature, and substrate UV-Vis spectrophotometer. Antagonistic test of the chitinase enzyme and endophytic bacterial isolates (isolate K4) Fusarium oxysporum. The results showed that bacterial isolate K4 had with chitinolytic index of 2.45 mm. Electrophoresis results with PCR 16s rRNA gene; the length of the amplified fragment is the position of 1300 bp. By doing the BLAST process in GenBank, the bacterial isolate has 97.93% similarity with Enterobacter cloacae. Then, this endophytic bacteria is called Enterobacter cloacae K4-G. This bacterium produced chitinase enzyme reaching maximum chitinase activity at the 38 hours with an activity of 0.0312 U/mL. The chitinase characterization results of E. cloacae K4-G showed that the optimum conditions were reached at at pH 6, temperature 45 ᵒC, and 2.5% substrate with a chitinase activity value of 0.2467 U/mL. Chitinase enzyme and bacteria Enterobacter cloacae K4-G can inhibit the growth of the fungus Fusarium oxysporum. Therefore, Chitinase from Enterobacter cloacae K4-G can be used as an antifungal pathogen in plants.
 
 Keywords: Chitinase, endophytic bacteria, Enterobacter cloacae

Recent Developments and Future Prospects of Natural Antimicrobial Bioactive Metabolites Obtained from Endophytic Bacterial Isolate

Background: Adathoda beddomei (Adosa), a kind of softwood, evergreen, perennial shrub, has been used as a source of endophyte bacteria. Adhatoda beddomei has a wide variety of chemicals, including anthocyanins, aminophylline, alkaloids, cardiac glycosides, isoprenaline, triterpenoids, resins, flavonoids, tannins, sterol, saponins, etc. The root, stem, and leaf parts of Adathoda beddomei are most often used in indigenous medicine. Moreover, the root bark is also used to cure several conditions, including leprosy, fever, and bleeding. Objective: Some important bioactive metabolites were obtained from endophytes bacteria and analyzed through various techniques (NMR, MASS, FTIR, HPLC, and UV- spectrophotometer) for their bioactive secondary metabolites. Methods: In silico calculation was performed to reveal bioactive metabolites with the potential to be antibacterial, and their primary mode of action may include dissolving bacterial and fungal cell walls. Results: The antimicrobial activity of Adathoda beddomei was demonstrated against different pathogenic and non-pathogenic bacteria. Identification of endophytes was done based on external morphological characteristics with the help of a scanning electron microscope (SEM). Conclusion: Natural compounds derived from endophyte bacteria with a very low molecular mass can be used to discover new and important structures for different pharmaceuticals and agrochemicals.

Indole acetic acid (IAA) production by endophytic bacterial isolate Agrobacterium tumefaciens BE-1 from roots of Musa acuminata

We have screened 23 endophytic isolates to estimate the production of indole acetic acid (IAA) from the root of the banana (Musa spp) by using Salkowski’s reagent spectrophotometric method with and without L- tryptophan supplement. Amongst 23 isolates only eight isolates, showed the ability to produce IAA. It is observed that one isolates out of eight produced maximum amount of IAA supplemented with and without L-tryptophan in medium. Based on morphological, cultural, biochemical and 16s rRNA gene sequencing method, this promising endophytic bacterial isolate (BE 1) was identified as Agrobacterium tumefaciens. IAA production of BE-1 was further confirmed by Thin-layer chromatography as well as by High-Performance Liquid Chromatography with and without L-tryptophan in medium. Statistical analysis was carried out using paired t-test to test whether the production of IAA significantly increased by using L-tryptophan in medium.

Efektivitas Bakteri Endofit Asal Lahan Basah untuk Menekan Penyakit Hawar Daun Bakteri (Xanthomonas oryzae) pada Padi Beras Merah (Oryza nivara L.)

Brown rice is a type of rice that has many benefits for the health of the body. The main diseases that attack many rice plants and cause a decrease in production include bacterial leaf blight (HDB) caused by the bacterium Xanthomonas oryzae. One alternative to control HDB is to use antagonistic agents, namely endophytic bacteria. This study aims to examine the ability of endophytic bacterial isolates from wetlands and the effect of application time in suppressing the intensity of bacterial leaf blight and to determine its effect on the growth of brown rice plants. There were 2 isolates of endophytic bacteria tested in this study, namely isolates of root origin (AKL) and isolates of stem origin (BLR) isolated from karamunting plants. This study used a completely randomized design (CRD) consisting of 5 treatments and 4 replications. The treatment used in this study was only the pathogen Xanthomonas Oryzae (control), soaking seeds with endophytic bacteria from roots, soaking seeds with endophytic bacteria from stems, soaking seeds + application when transplanting with endophytic bacteria from roots and seed soaking + application when transplanting Plant with stem-origin endophytic bacteria. Treatment of endophytic bacteria on brown rice seeds and application during transplanting was able to reduce the intensity of bacterial leaf blight (X. oryzae) with a disease intensity of 83% and an effectiveness of 15.6%. Treatment of endophytic bacteria on rice seeds did not inhibit seed germination and was able to increase the number of tillers, but had not been able to affect the increase in plant height.

The Potential of Endophytic Bacteria in Controlling Cylindrocladium sp., The Cause of Leaf Blight on Eucalyptus pellita Seedlings by In-Vitro

Cylindrocladium sp is a fungus that causes leaf blight on Eucalyptus pellita seedlings. Endophytic bacteria are an alternative biological control that can reduce the risk of environmental pollution and reduce resistance by pathogens. This research aims to obtain endophytic bacteria that have potential as biocontrol agents and to characterize isolates that inhibit more than 30%. Testing was carried out using the dual culture method on Potato Sucrose Agar (PSA) media. The results of the antagonism test showed that the endophytic bacterial isolates E320 and E323 were able to form an inhibition zone of more than 30%, namely 38.79% and 41.25% and had the potential to act as biocontrol agents for Cylindrocladium sp., which causes leaf blight on eucalyptus. The characteristics of isolate E320 were that it was able to produce protease, cellulase and siderophore activities, while isolate E323 was only able to produce protease

Antibacterial Ability of Seaweed Endophytic Bacteria (Turbinaria ornata, Sargassum crassifolium, and Sargassum polycystum) Against Skin Disease Agents

Bioactive substances that can prevent the growth of pathogenic germs can be produced by endophytic bacteria This study aims to identify seaweed endophytic bacteria (Turbinaria ornata, Sargassum crassifolium, Sargassum polycystum) and their potential antibacterial activity against skin disease agents (Staphylococcus aureus and Staphylococcus epidermidis). In February 2023 (the rainy season), seaweed was harvested from the waters off Panjang Island in Jepara Regency, Central Java, Indonesia. Endophytic bacterial isolates that had been effectively isolated and purified were directly tested for antibacterial activity. Three isolates with the best antibacterial activity were extracted using the ethyl acetate solvent. The extract samples will be put through additional antibacterial testing using the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and paper disc diffusion procedures. Using the thin layer chromatography (TLC), the class of chemical components in the extract was determined. A molecular technique based on the 16s rRNA gene (1,400 bp) was used to identify endophytic bacterial isolates. Three species of seaweed yielded 25 isolates of endophytic bacteria: 11 from T. ornata, 7 from S. crassifolium, and 7 from S. polycystum. To.09.pp, To.10.pp, and Sc.06.pp were the 3 isolates with the highest antibacterial activity in the direct challenge test. Zone of inhibition results from subsequent antibacterial testing using paper disc diffusion ranged from medium to very strong intensity. To.10.pp sample’s MIC test yielded the best results, with S. aureus and S. epidermidis concentrations of 937.5 and 1,875 µg/mL, respectively. MBC test yielded the highest findings, with S. aureus and S. epidermidis concentrations of 1,875 and 1,875 µg/mL, respectively. The To.10.pp sample yielded terpenoids, alkaloids, and flavonoids, according to TLC analysis of chemical constituent groups. Acinetobacter indicus strain 80-1-2 and Vibrio harveyi strain B14-1 were identified as potential endophytic bacteria from T. ornata, and Acinetobacter indicus strain 80-1-2 from S. crassifolium. HIGHLIGHTS Endophytic seaweed Turbinaria ornata, Sargassum crassifolium, and Sargassum polycystum showed antibacterial activity against Staphylococcus aureus ATCC 29213 and Staphylococcus epidermidis FNCC 0048 Acinetobacter indicus strain 80-1-2, and Vibrio harveyi strain B14-1 were all successfully identified by molecular analysis as potential endophytic bacteria Identification of compounds using Thin Layer Chromatography (TLC) showed the presence of terpenoids, alkaloids, and flavonoids GRAPHICAL ABSTRACT

Potential of Endophytic Bacteria in Controlling The Red Jabon Leaf Spot Pathogens In Vitro

Plant pathogens pose a significant challenge to the cultivation of red Jabon (Anthocephalus macrophyllus) seedlings. Notably, the fungi Rhizoctonia sp. and Pestalotia sp. are responsible for the destructive red leaf spot disease on Jabon leaves. To combat these fungal pathogens, the use of endophytic bacteria has emerged as a potential alternative. Endophytic bacteria can be isolated from various plant sources, although their effectiveness in controlling forest plant pathogens like Jabon has not been thoroughly explored. This study aimed to assess the potential of endophytic bacterial isolates obtained from Pteris ensiformis (Isolates APE15, APE22, APE33, and APE35) in controlling the growth of Rhizoctonia sp. and Pestalotia sp. through in vitro experiments. The antibiosis activity of the endophytic bacteria against the pathogenic fungi was evaluated using the dual culture method on PDA media. The results revealed that among the four endophytic bacterial isolates, APE35 exhibited the highest inhibitory effect on Rhizoctonia sp. (86.79%) and Pestalotia sp. (67.5%), while isolate APE22 only inhibited the growth of Pestalotia sp. (55%). In contrast, isolates APE15 and APE33 were unable to suppress either fungus. The antibiosis activity of APE35 and APE22 resulted in abnormal hyphal growth of the pathogenic fungi, characterized by shriveled, bent, dark-colored, and coiled hyphae. Physiological characterization of the endophytic bacteria revealed their ability to produce protease, cellulase, catalase, and phosphate-dissolving enzymes. Additionally, these bacteria exhibited a Gram-positive nature. This study provides valuable insights into the potential of endophytic bacterial isolates from P. ensiformis (APE35 and APE22) as biological control agents for Rhizoctonia sp. and Pestalotia sp., the causative agents of red Jabon leaf spot disease.

Can Phytoremediation-Induced Changes in the Microbiome Improve Saline/Sodic Soil and Plant Health?

Increasing soil salinity and/or sodicity is an expanding problem in the Northern Great Plains (NGP) of North America. This study investigated the impact of phytoremediation on the soil microbiome and if changes, in turn, had positive or negative effects on plant establishment. Amplicon sequencing and gas chromatograph/mass spectrometer analysis compared root metabolites and microbial composition of bulk vs. rhizosphere soils between two soil types (productive and saline/sodic). Beta-diversity analysis indicated that bacterial and fungal communities from both the bulk and rhizosphere soils from each soil type clustered separately, indicating dissimilar microbial composition. Plant species also influenced both root-associated bacterial and fungal communities with separate clustering of operational taxonomic units (OTUs) identified. Canonical correlation analysis (CCA) found a clear association between specific soil characteristics and soil types. Bacterial and fungal OTUs from productive soil were correlated with greater %Ca Sat, %H Sat, and potassium (ppm), especially for OTUs differentially enriched in productive soil. Both bacterial and fungal OTUs from saline/sodic soil are associated with increased Ca (ppm), soil pH, %Na Sat and CEC. Metabolite analysis showed that kochia (Bassia scoparia) roots from the saline/sodic soil had a 4.4-fold decrease in pantothenate accumulation (p = 0.004). Moreover, two endophytic bacterial isolates, a Bacillus spp. and a previously uncultured halophile, isolated from creeping foxtail (Alopecurus arundinaceus) grown in saline/sodic soil and used as buckwheat (Fagopyrum esculentum) seed inoculants, significantly increased seed germination by >30% and vigor index by 0.2 under osmotic stress (0.2 M NaCl) (p < 0.05). This study revealed the importance of soil, root-associated, and endophytic microbiomes. Using native microbes as seed inoculants may help in establishment and growth of species used for phytoremediation of saline/sodic soil.

Diversity of endophytic bacteria isolated from mangrove Bruguiera gymnorrhiza (L.) Lam.) and Rhizopora mucronata Poir. originated from Enggano island

Endophytic bacteria are bacteria that live colonizing in plant tissues without causing harmful effects. Endophytic bacteria are found in the vascular tissues of plant, including mangroves (B. gymnorrhiza (L.) Lam. ) and R. mucronata Poir.). Mangroves have numerous advantages, one of them is as a medicinal plant. This study aims to obtain the diversity of endophytic bacteria isolated from Enggano Island mangroves (B. gymnorrhiza (L.) Lam. and R. mucronata Poir.). Endophytic bacteria were isolated using the grinding method through which the surface was sterilized with natrium hypochlorite and alcohol 70%. The obtained isolates were then identified in terms of morphological characters, Gram staining, and then biochemical tests. A total of 40 bacterial isolates were successfully isolated from the roots, stems, and leaves of both mangrove species. It was observed that 20 endophytic bacterial isolates were associated with mangrove B. gymnorrhiza (L.) Lam., while the remaining 20 isolates were from R. mucronata Poir. Based on morphological observation, Gram staining, and a series of biochemical tests, those 40 isolates were found to to be closely related with Bacilus, Micrococcus, and Pseudomonas. To conclude, B. gymnorrhiza (L.) Lam. and R. mucronata Poir. have a high diversity in endophytic bacteria.

Isolation and Identification of Endophytic Bacterial Isolates from the Leaves, Roots, and Stems Parts of Artemisia annua, Moringa oleifera, and Ocimum lamiifolium Plants.

Medicinal plants are known to harbor diverse species of endophytic bacteria which are known for secretion of beneficial secondary metabolites, like enzymes and antimicrobial compounds. The present study aimed to isolate, characterize, and identify the endophytic bacteria isolates from Artemisia annua, Moringa oleifera, and Ocimum lamiifolium plants. Certain endophytic bacterial isolates were screened. Phosphate and Zinc solubilization were performed for newly obtained isolates. The 16S rRNA gene sequencing was performed for RPAAI-8 isolate. Data were analyzed. Our study showed that endophytic bacterial isolates were recognized to be Bacillus cereus, B. subtilis, Citrobacter freundii, Enterobacter asburiae, E. cloacae, E. kobei, E. ludwigii, Enterococcus faecium, and Pseudomonas monteilli. From among these differentiated endophytic bacterial isolates, Enterobacter species are the most frequently obtained isolates. These bacterial isolates were shown 99.77% sequence similarity to Enterobacter ludwigii EN-119T (JTLO01000001) using 16S rRNA gene sequencing. This isolate was designated as Enterobacter sp. RPAAI-8. This isolate was able to employ selected cheap and cost-effective agro wastes as a carbon source. This cheap agro waste utilization by these Enterobacter species could be the first report. In conclusion, the present isolates are found to be employed for plant growth promotion and solubilizing insoluble phosphate and zinc. Before this time, most of the recent isolates were not identified from these medicinal plants. The ethyl acetate extract of the isolates also showed inhibitory activity against selected test pathogens.

Plant-Disease-Suppressive and Growth-Promoting Activities of Endophytic and Rhizobacterial Isolates Associated with Citrullus colocynthis.

This study was conducted to investigate the antagonistic potential of endophytic and rhizospheric bacterial isolates obtained from Citrullus colocynthis in suppressing Fusarium solani and Pythium aphanidermatum and promoting the growth of cucumber. Molecular identification of bacterial strains associated with C. colocynthis confirmed that these strains belong to the Achromobacter, Pantoea, Pseudomonas, Rhizobium, Sphingobacterium, Bacillus, Sinorhizobium, Staphylococcus, Cupriavidus, and Exiguobacterium genera. A dual culture assay showed that nine of the bacterial strains exhibited antifungal activity, four of which were effective against both pathogens. Strains B27 (Pantoea dispersa) and B28 (Exiguobacterium indicum) caused the highest percentage of inhibition towards F. solani (48.5% and 48.1%, respectively). P. aphanidermatum growth was impeded by the B21 (Bacillus cereus, 44.7%) and B28 (Exiguobacterium indicum, 51.1%) strains. Scanning electron microscopy showed that the strains caused abnormality in phytopathogens' mycelia. All of the selected bacterial strains showed good IAA production (>500 ppm). A paper towel experiment demonstrated that these strains improved the seed germination, root/shoot growth, and vigor index of cucumber seedlings. Our findings suggest that the bacterial strains from C. colocynthis are suppressive to F. solani and P. aphanidermatum and can promote cucumber growth. This appears to be the first study to report the efficacy of these bacterial strains from C. colocynthis against F. solani and P. aphanidermatum.

An endophytic Paenibacillus polymyxa hg18 and its biocontrol potential against Fusarium oxysporum f. sp. cucumerinum

Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum is a serious fungal, soil-borne disease that has a dramtic negative impact on the yield and quality of cucumber. In this study, isolates of endophytic bacteria isolated from healthy cucumber plants were evaluated for their ability to inhibit Fusarium wilt. Results indicated that 6 out of 100 of the obtained endophytic bacterial isolates exhibited significant inhibitory activity against mycelial development of F. oxysporum f. sp. cucumerinum, with an inhibition rate > 60 % in dual culture assays. Among the active isolates, strain hg18 exhibited the strongest activity with a 69.57 % rate of inhibition. Strain hg18 was identified as Paenibacillus polymyxa based on morphological, physiological, and biochemical traits, as well as a phylogenetic tree that was constructed using 16S rRNA and rpoB gene sequences. Biological and PCR assays demonstrated that strain hg18 can secrete IAA, a siderophore, hydrolytic enzymes, including protease, cellulase and glucanase, and antimicrobial compounds, such as iturin, fengycin, and non-ribosomal polypeptide synthase, as well as fix nitrogen. Strain hg18 decreased the disease index of cucumber Fusarium wilt and promoted cucumber growth in non-diseased plants in greenhouse experiments, compared to a water treatment. These findings demonstrate the potential of using P. polymyxa hg18 as a biocontrol agent for controlling Fusarium wilt in cucumber.

Detection of bacterial pathogen on corn plants and test the potential of endophytic microbes to controlling stewart wilt disease in vitro

The use of synthetic pesticides to increase maize production sustainably contributes to increasing the development of pathogens and tends to be less effective in environmental conditions that support pathogens. In addition, the emergence of environmental pollution due to the use of chemicals causes the need for environmentally-friendly control technologies. Endophytic microbes are biological agents that can be used to plant disease control that is environmentally friendly and practical in their application. The study aimed to detect pathogenic bacteria that cause wilt and blight in maize and then examine the potential of several endophytic microbial isolates in controlling Stewart wilt pathogens in maize in vitro. The research was carried out from February to July 2021 at the Cereal Crop Research Institute Laboratory in Maros for morphological identification and microbial potential testing, while serological tests were carried out at the Makassar Plant Quarantine Laboratory, South Sulawesi. The study began with detecting pathogenic bacteria serologically using the Enzyme-Linked Immunosorbent Assay (ELISA) method. The results showed that blight symptoms on corn isolated from the experimental garden of IP2TP Bajeng Gowa Regency PS-4 and PS-5 were detected as bacteria Pantoea stewartii subsp. stewartii. The antagonistic test of endophytic bacterial isolates I.A1, II.D1, III.A2, IV.B2, and endophytic fungi isolates AC-1, AC-3, and DC-5 was able to suppress the growth of pathogenic bacteria isolates PS-4 and PS-5 The growth suppression of pathogenic bacteria was observed by forming inhibitory zones of antibiosis compounds. Pathogenic bacteria Pantoea stewartii subsp. stewartii can be controlled using endophytic microbes.

In vitro antagonism test of endophytic isolates from the ciplukan plant (Physalis angulata L.) against Ralstonia solanacearums

Ralstonia solanacearum was a pathogenic bacteria that causes wilt disease which can cause up to one hundred percent damage to horticultural plants. Therefore, a control effort was needed to overcome this problem. The use of pesticides was an alternative that can be used to suppress the growth of the pathogen R. solanacearum. However, its continuous use poses a high risk to the environment so friendly and safe control efforts are needed. One way was by utilizing endophytic bacteria. This study aims to test the ability of endophytic bacterial isolates from ciplukan plant (Physalis angulata L.) to suppress the growth of the pathogenic bacteria R. solanacearum in vitro. The method in this research includes rejuvenating endophytic bacterial isolates BA2(3), BA3(1), DA1(4) and BU3(5) from ciplukan plants (Physalis angulata L.) obtained from research conducted by Setianah (2020), observations macroscopic and microscopic endophyte isolates, hypersensitivity test of endophytic bacteria on tobacco plants (Nicotiana tabacum L.), then continued with an in vitro antagonist test using the Kirby Baurer technique. Research data shows that of the four candidates, two isolates of endophytic bacteria, namely BA2(3) and BU3(5), showed a negative hypersensitivity reaction which was characterized by the absence of necrosis symptoms in the hypersensitivity test, so these isolates could be tested for antagonists. The results of the antagonist test showed that isolates BA2(3) and BU3(5) had the potential to inhibit the growth of R. solanacearum which had an inhibitory diameter of 3.03 mm and 1.60 mm in the first 24 hours of incubation. It is hoped that the ability of endophyte isolates BA2(3) and BU3(5) to inhibit the growth of the pathogen R. solanacearum can be used as a biological agent to reduce the use of pesticides in treating plant diseases.

Exploring the mechanisms of endophytic bacteria for suppressing early blight disease in tomato (Solanum lycopersicum L.).

Controlling early blight of tomatoes using endophytic bacteria is an eco-friendly and sustainable approach to manage this common fungal disease caused by Alternaria solani, Alternaria alternata, and Curvularia lunata. Endophytic bacteria are microorganisms that live inside plant tissues without causing harm and can help protect the host plant from pathogens. In this work, twenty endophytic bacterial isolates from tomato healthy plants were tested against pathogenic fungal isolates that caused early blight disease in vitro. Out of the 20 tested isolates, three (B4, B7, and B17) were considered effective isolates against the growth of fungal pathogens. The three isolates were recognized as Enterobacter cloacae HS-6 (B4), Pseudomonas gessardii HS-5 (B 7), and Pseudomonas mediterranea HS-4 (B17) using 16s-rDNA sequencing. Different concentrations of bacterial cultural diltrates at 20, 40, and 60% were tested for their antagonistic effects on the development of pathogenic fungi in vitro. The lowest dry weights of pathogenic isolates in all bacterial culture filtrates were discovered at 60%. In all culture filtrates, phenolic compounds showed the largest peak area. Under greenhouse conditions, the least disease severity of tomato early blight was found for E. cloacae and its culture filtrate compared to other treatments. Real-time PCR was used to examine the expression pattern of the defense response gene β-1.3 glucanase gene in infected tomato plants with pathogenic fungi (control) as well as its relations with efficient biocontrol agent (E. cloacae). The expression of the gene increased substantially and significantly after three days from the inoculation-infected plants with C. lunata and E. cloacae while it reached the maximum after five days from the inoculation with A. alternata, A. solani and E. cloacae. Our study concluded that the endophytic bacterial isolate E. cloacae can be considered a promising biocontrol agent for preventing tomato early blight.

Antifungal Activity of Endophytic Bacteria Isolated from Miana Plants (Coleus scutellarioides (L.) Benth.) against Candida albicans

Highlights: 1.Due to the adverse effects associated with current antifungal drugs, research on traditional medicine is necessary to explore other options for candidiasis treatment.2.Following the findings of this study, it is recommended to conduct further research by incorporating Coleus scuttellarioides filtrate into the growth medium, since this may improve bacterial growth by producing optimal secondary metabolites. Abstract Candida albicans is the most common organism responsible for both mucosal and systemic infections, accounting for approximately 70% of fungal infections worldwide. Miana, scientifically known as Coleus scuttellarioides (L.) Benth., is recognized for its use in traditional medicinal practices. Miana plants contain endophytic bacteria that possess the ability to produce secondary metabolites with potential antifungal agents. The objective of this study was to assess the antifungal activity of nine endophytic bacteria isolates derived from Coleus scuttellarioides against Candida albicans. This study was laboratory-based qualitative experimental research that applied the Kirby-Bauer diffusion method and several modifications. The Candida albicans specimens were spread throughout the entire potato dextrose agar medium. Afterwards, paper discs that had been soaked in a liquid culture of endophytic bacterial isolates were carefully placed on the surface of the medium. The complete setup was then incubated for 1–2 days. The potential antifungal activity of endophytic bacteria was assessed by observing the emergence of a clear zone surrounding their growth, which would indicate inhibition. An additional observation was performed in the follow-up test, involving the use of Sabouraud dextrose agar medium to confirm the initial test result. The results from the inhibitory test revealed that none of the bacterial isolates exhibited any inhibition zone. Conversely, ketoconazole as the positive control showed an inhibition zone with an average diameter of 28.5 mm. In conclusion, endophytic bacterial isolates obtained from Coleus scuttellarioides have no discernible antifungal properties against Candida albicans. This study implies that ketoconazole remains effective in treating infections caused by Candida albicans.

Identification of Cultured and Diazotrophic Bacterial Endophytes in Warm-Season Grasses

Endophytes can have positive effects on plant health and growth, but endophytes of warm-season grasses are largely understudied, and inocula are rarely applied to cultivated grasses. To identify endophytes in warm-season grasses, 35 endophytic bacterial isolates were cultured from the roots, rhizomes, and shoots of bermudagrass ( Cynodon dactylon), energy cane ( Saccharum spp.), Johnsongrass ( Sorghum halepense), napiergrass ( Cenchrus purpureus), perennial sorghum ( Sorghum bicolor × S. halepense), sorghum ( Sorghum bicolor), sorghum × sudangrass ( Sorghum × drummondii), and peanut (outgroup). Sequencing of the 16S rRNA fragment from the endophytes revealed that the bacterial sequences were similar to Bacillus spp. (19 isolates), Burkholderia spp. (4), Pantoea spp. (4), Pseudomonas spp. (3), Enterobacter spp. (2), Kosakonia spp . (2), and Sphingomonas sp. (1). To identify diazotrophic endophytes, DNA isolated from surface-disinfected tissue from warm-season grasses was used to amplify nifH. Bacteria containing nifH were similar to 13 genera, and sequences similar to Pseudolabrys sp. were present in the greatest number of warm-season grasses. Bacteria similar to Bradyrhizobium frederickii strain CNPSo 3447 were identified frequently from the leaves and roots of sorghum × sudangrass (and peanut roots). Using similarity to known nifH fragments, six genera were identified that had not been previously identified in grasses. Thus, a large number of endophytes were found in warm-season grasses and could enhance plant growth or grass nitrogen levels by using nitrogen fixation. [Formula: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2023.

Molecular characterization and in silico evaluation of surfactins produced by endophytic bacteria from Phanera splendens.

The Phanera splendens (Kunth) Vaz. is a medicinal plant that is used in traditional medicine for the treatment of various diseases, such as malaria. This plant presents highly efficient endophytic bacterial isolates with biocontrol properties. Bacillus sp. is responsible for the production of a variety of non-ribosomal synthesized cyclic lipopeptides which highlight the surfactins. Surfactins have a wide range of antimicrobial activity, including antiplasmodial activity. There is scientific evidence that surfactin structure 2d-01 can be a potent inhibitor against a Plasmodium falciparum sirtuin (Sir2) by acting on the Sir2A protein as the target. The Pf genome encodes two known sirtuins, PfSir2A and PfSir2B, where PfSir2A is a regulator of asexual growth and var gene expression. Herein, we have identified six surfactins produced by endophytic bacteria and performed in silico analysis to elucidate the binding mode of surfactins at the active site of the PfSir2A enzyme. Among the characterized surfactins, 1d-02 showed the highest affinity for the PfSir2A enzyme, with binding energy values equal to -45.08 ± 6.0 and -11.95 ± 0.8kcal/mol, using MM/GBSA and SIE methods, respectively. We hope that the information about the surfactin structures obtained in this work, as well as the potential binding affinity with an important enzyme from P. falciparum, could contribute to the design of new compounds with antimalarial activity.

Isolation of Endophytic Bacteria from Cavendish Banana pseudostem (Musa acuminata) and Plant Growth Promoting Characterization

Banana endophytic bacteria have many plant growth promoting activities and the enhanced influences based on the capable of endophytic colonization. Previous studies have mainly focused on endophytic bacteria in banana leaves, roots and shoots. This study aimed to evaluate the potential application of endophytic bacteria isolated from pseudostem of Cavendish banana. Eighteen endophytic bacterial isolates were collected from eight pseudostem samples. The tests showed that the indigenous endophytic bacteria, depending on the isolate, could dissolve insoluble inorganic minerals, produce extracellular hydrolytic enzymes, produce indole-3-acetic acid, fix nitrogen and control Phyllosticta sp. and Fusarium sp. Preliminary safety tests showed that one isolate did not exhibit hemolytic activity. Many isolates were compatible with each other, especially four strains including TC4.1, TC5.1, TC6.2 and TD7.1 were compatible with all remaining isolate and suitable for developing multi-strain products. Growth curves indicated that two isolates, TD7.2 and LA7.4, peaked at 16 and 18 hours respectively. The results showed that these endophytic bacteria have many potential activities. However, other plant growth promoting activities should be assessed in order to have potential applications as well as to exploit these bacteria.

Hemolysis and hypersensitive tests ease culture collection management of antagonistic bacteria

A biosafety assessment is a crucial first step in the management of microbial culture collection to screen and determine unexpected potential plant and human pathogenic bacteria. It is common to collect and store as many fresh culture collections from natural resources before being further evaluated for antagonist bacteria. As a result, a bulk of isolates must be preserved which required more effort and budget. Safety evaluations based on the hemolysis and hypersensitive reactions offer simple tests to ease culture collection management of antagonist bacteria. The study aimed to evaluate the safety of bacterial culture collection for their hemolysis and hypersensitive reactions. Ninety-five isolates of rhizosphere and endophytic bacterial isolates from the culture collections of the Department of Plant Protection-IPB University, Indonesian Industrial and Beverages Crops Research Institute, and Indonesian Spice and Medicinal Crops Research Institute, were evaluated their safety using the hemolysis and hypersensitive tests. The hemolysis test was conducted using blood agar media, from which isolates with a negative (?) reaction were then tested for the hypersensitivity reaction on tobacco leaves. Bacterial isolates passed from both hemolysis and hypersensitivity tests were then preserved by the lyophilization method for long-term storage of culture collection. Based on the hemolysis test, 68 out of 95 bacterial isolates (71.57%) were found to be positive (? or ?) reactions. The hypersensitive test showed that 22 of 27 negative hemolysis isolates did not trigger hypersensitivity reactions in tobacco leaves, therefore, they were preserved by lyophilization. The study indicated that a high number of bacterial isolates in the present collection, 68 positive hemolysis, and 5 hypersensitive, need to be re-evaluated due to their safety concerns. The present study highlights the importance of biosafety tests performed in an early stage before the to permanent collection of antagonist isolates.