Antibiotic-producing Bacteria Research Articles

Rhizosphere actinobacteria isolated from Pometia pinnata and its antimicrobial activity

Abstract. Janatiningrum I, Zahra A, Fitriyanti, Anggia V. 2024. Rhizosphere actinobacteria isolated from Pometia pinnata and its antimicrobial activity. Biodiversitas 25: 1007-1014. Actinobacteria are currently the largest antibiotic-producing bacteria due to their extreme environments such as soil, roots and rhizosphere. The diversity of rhizosphere actinobacteria is affected by plant exudates. Pometia pinnata is a plant that has long been used for traditional medicine in Indonesia. This study was aimed at isolating and evaluating isolate and evaluate the actinobacteria rhizosphere of P. pinnata, to screen their antibacterial and antifungal properties. Isolation of actinobacteria was done by using serial dilution method and grown on media. About 34 actinobacteria were successfully isolated from the rhizosphere of P. pinnata and 50% of them showed index antimicrobial activity for Staphylococcus aureus ATCC 6538 (0.52), Streptococcus pneumoniae ATCC 1705 (2.87), and Escherichia coli ATCC 25922 (1.28). Several microbial isolated microbes (20.8%) were found capable in inhibiting fungal growth. The highest antibacterial activity against all bacteria was shown by RM12 isolate. The aqueous fraction of RM12 isolate demonstrated a significant inhibitory activity against S. aureus ATCC 6538 and E. coli ATCC 25922 at concentrations of 250 ppm, 500 ppm and 1000 ppm. TLC bioautography showed that aqueous fraction RM 12 do not belong to the polyphenol or phenol compound group. The RM12 was characterized by using 16S ribosomal RNA sequence found to belong to actinobacteria genera to Streptomyces bungoensis.

Abstract 1452 Testing for Antibiotic Producing Bacteria in Soil

Abstract 1452 Testing for Antibiotic Producing Bacteria in Soil

Isolation, whole-genome sequencing, and annotation of two antibiotic-producing and antibiotic-resistant bacteria, Pantoea rodasii RIT 836 and Pseudomonas endophytica RIT 838, collected from the environment.

Antimicrobial resistance (AMR) is a global threat to human health since infections caused by antimicrobial-resistant bacteria are life-threatening conditions with minimal treatment options. Bacteria become resistant when they develop the ability to overcome the compounds that are meant to kill them, i.e., antibiotics. The increasing number of resistant pathogens worldwide is contrasted by the slow progress in the discovery and production of new antibiotics. About 700,000 global deaths per year are estimated as a result of drug-resistant infections, which could escalate to nearly 10 million by 2050 if we fail to address the AMR challenge. In this study, we collected and isolated bacteria from the environment to screen for antibiotic resistance. We identified several bacteria that showed resistance to multiple clinically relevant antibiotics when tested in antibiotic susceptibility disk assays. We also found that two strains, identified as Pantoea rodasii RIT 836 and Pseudomonas endophytica RIT 838 via whole genome sequencing and annotation, produce bactericidal compounds against both Gram-positive and Gram-negative bacteria in disc-diffusion inhibitory assays. We mined the two strains' whole-genome sequences to gain more information and insights into the antibiotic resistance and production by these bacteria. Subsequently, we aim to isolate, identify, and further characterize the novel antibiotic compounds detected in our assays and bioinformatics analysis.

Industrial and Pharmaceutical Applications of Microbial Diversity of Hypersaline Ecology from Lonar Soda Crater.

The unidentified geochemical and physiochemical characteristics of Soda Lakes across the globe make it a novel reservoir and bring attention to scientific civic for its conceivable industrial and pharmaceutical applications. In India, in the Maharashtra state, Lonar Lake is a naturally created Soda Lake by a meteorite impact. Phylogenetic data from this lake explored a diverse array of microorganisms like haloalkaliphilic bacteria and Archaea. Previously reported studies postulated the major microbial communities present in this lake ecosystem are Proteobacteria, Actinobacteria, Firmicutes, and Cyanobacteria. Furthermore, it also contains Bacteroidetes, Nitrospirae, and Verrucomicrobia. This lake is also rich in phytoplankton, with the predominant presence of the Spirulina plantensis. Unique microbial strains from Lonar Lake ecosystems have fascinated consideration as a source of biological molecules with medicinal, industrial, and biotechnological potential. Recent literature revealed the isolation of antibioticproducing bacteria and alkaline proteases-producing alkaliphilic bacterium, as well as novel species of rare methylotrophs, other bacterial strains involved in producing vital enzymes, and unique actinomycetes are also reported. It indicates that the novel bacterial assemblage not reached hitherto may exist in this modified and unique ecology. This comprehensive review provides information about microbial diversity and its industrial and pharmaceutical interests that exist in Lonar Lake, which could be the future source of bioactive enzymes, biosurfactants, and biofuel and also useful in bioremediation. Furthermore, the novel species of microorganisms isolated from Lonar Lake have applications in the biosynthesis of medicines like antibiotics, antivirals, antifungals, anti-inflammatory agents, and precursors for synthesising valuable products. Data consolidated in the present review will cater to the needs of emerging industrial sectors for their commercial and therapeutic applications.

Insects and their antibiotic-producing bacteria

Many, if not all, plants and animals form mutually beneficial symbioses (mutualisms) with microbes and a subset of these mutualisms are defensive, in which the host provides food and housing in return for defence against disease. These symbioses typically involve antibiotic-producing bacteria, the best known of which are filamentous actinomycetes in the genera Streptomyces and Pseudonocardia and unicellular species in the genus Pseudomonas. Such mutualisms are likely to be widespread in nature, but they are best characterised in insects, which provide experimentally tractable models for studying symbiosis and microbiome formation because they typically host less complex microbial communities. Here, we examine the mutualisms formed between insects and antibiotic-producing bacteria using well-characterised examples, including digger wasps and their endosymbiotic Streptomyces species, attine ants and their mutualist Pseudonocardia species and Paederus beetles with their pederin-producing Pseudomonas species. We also discuss how searching such symbiotic niches can give insights into the evolution and functions of microbial specialised metabolites and provide new platforms for antibiotic discovery.

Impact of Diameter of Inhibition in Crowded Plates on the in vitro Inhibitory Strength of Potential Antibiotic-Producing Bacteria Isolated from Some Natural Habitats

Antimicrobial resistance is a global problem, and efforts to replace failing antibiotics are crucial. We investigated the impact of the diameter of inhibition (mm) in crowded plates of potential antibiotic-producing bacteria on their in-vitro inhibitory strength. Our previous research identified 12 potential antibiotic-producing bacteria from natural habitats and obtained their diameters of inhibition in preliminary crowded plates. The potential candidates were further challenged with some pathogenic microbes by the Agar-well diffusion technique to test their strength. The results showed that the diameter of inhibition of the potential antibiotic-producing isolates obtained at the crowded plate technique level was not a predictor of the potency of potential antibiotic-producing bacteria (rs = 0.52, P = 0.08). In summary, the selection of potent candidate microbes for the development of new antimicrobial compounds against multidrug-resistant pathogens cannot be determined based on the diameter of inhibition in a preliminary investigation using the crowded plate technique. Further studies involving complementary techniques are necessary to determine the best potential candidate organisms for the development of novel antimicrobial compounds.

Comparative metataxonamic analyses of seeds and leaves of traditional varieties and hybrids of cucumber (Cucumis sativus L.) reveals distinct and core microbiome

Profiling the endophytic microbiome of different tissues and varieties of agricultural crops can help to understand i) the tissue specific and varietal specific microbes associated with the plants ii) their potential role in growth, stress tolerance, disease resistance, and yield of the plants. Comparative microbiome profiling across various varieties and hybrids will also be useful to identify the plant's core microbiome. The main objective of the work is to profile and study the microbiome of traditional varieties in comparison with hybrids of cucumber, which would help to understand the microbiome structure in developing consortia to engineer the microbiome of modern hybrids, for useful phenotypes. Metataxonomic sequencing of bacteria and fungi using 16S rRNA gene and ITS regions respectively were carried out in seed and leaf samples of cucumber traditional varieties and modern hybrids. Among bacteria, Prevotella, Bacteroides, Lactobacillus, Dialester, and Fecalibacterium, and among fungal genera, Pichia, Aspergillus, Phaeoisariopsis, Candida, and Malassezia belonged to the core microbiome of cucumber. Modern hybrids were rich in antibiotic producing and toxic pollutant degrading bacteria. Many of the fungi and bacteria observed in the study are well known plant growth promoting microorganisms and play role in offering disease resistance. Some of the bacteria and fungi have beneficial roles in human gut thus revealing the dietary importance of cucumber. The microbes identified in the current study will be useful starting point to develop a consortia to engineer the cucumber microbiome for growth, yield and stress tolerance traits.

Enhancing the Antibiotic Production by Thermophilic Bacteria Isolated from Hot Spring Waters via Ethyl Methanesulfonate Mutagenesis.

Antibiotic-resistant bacteria represent a serious public health threat. For that reason, the development of new and effective antibiotics to control pathogens has become necessary. The current study aims to search for new microorganisms expressing antibiotic production capacity. Fifteen sites covering a wide range of harsh environmental conditions in Egypt were investigated. Two hundred and eighty bacterial isolates were obtained and then tested against pathogenic bacteria using the agar disk diffusion technique. Fifty-two (18.6% of the total) of the isolates exhibited antagonistic properties, which affected one or more of the tested pathogens. The isolate 113 was identified as Bacillus licheniformis and isolate 10 was identified as Brevibacillus borstelensis using the 16S rRNA technique. The B. licheniformis strain was stronger in antibiotic production against S. typhi, M. luteus, and P. ariginosa, whereas the strain Br. borstelensis was more efficient against B. cereus, E. coli, and Klebs. sp. The sensitivity of the strains to commercial antibiotics showed that B. licheniformis was highly sensitive to seven commercial antibiotics, whereas Br. borstelensis was sensitive to nine antibiotics. The two strains were subjected to ethyl methanesulfonate (EMS) mutagenesis to obtain mutants with a higher antibiotic production. The total bacterial count was measured after treatment with EMS mutagen and showed a significant gradual increase in the antimicrobial activity, which was achieved via shaking in the presence of EMS for 60 min. High antimicrobial activities were noted with 17 and 14 mutants from the B. licheniformis and Br. borstelensis strains, respectively. The mutant B. licheniformis (M15/Amo) was more active than the parent strain against S. aureus (212.5%), while the mutant Br. borstelensis (B7/Neo) was more effective against S. typhi (83.3%). The present study demonstrates the possibility of obtaining potent antibiotic-producing bacteria in hot spring waters and further improving the indigenous bacterial capacity to produce antibiotics by using EMS mutagenesis.

Isolation and Characterization of Antibiotic-producing Bacteria from the Salt Range of Kallar Kahar, Pakistan

Isolation and Characterization of Antibiotic-producing Bacteria from the Salt Range of Kallar Kahar, Pakistan

Production of antibacterial compounds using Bacillus spp. isolated from thermal springs in Saudi Arabia

Seventeen water samples were collected from four different thermal springs in Saudi Arabia. Microbiological assays were used to assess the antibacterial activities of bacterial colonies against antibiotic-resistant and susceptible-bacterial strains, and 16S rRNA gene sequencing was used to identify the genus and species of these antibiotic-producing bacteria. Chromatography and spectroscopy were used to separate the active compounds and help figuring out what their structures were. Four compounds were isolated using bacteria: N-acetyltryptamine (1), isovaleric acid (2), ethyl-4-ethoxybenzoate (3) and phenylacetic acid (4). Compounds 1, 2 and 4 were produced from Bacillus pumilus and 3 was from Bacillus licheniformis (AH-E1). The outcomes of the minimum inhibitory concentrations (MICs) showed that all pure compounds produced in this work had antibacterial activities against Gram-positive pathogens (between 128 mg/L and 512 mg/L compared to the control) and compound 2 had activity against E. coli.

LexR Positively Regulates the LexABC Efflux Pump Involved in Self-Resistance to the Antimicrobial Di-N-Oxide Phenazine in Lysobacter antibioticus.

Myxin, a di-N-oxide phenazine isolated from the soil bacterium Lysobacter antibioticus, exhibits potent activity against various microorganisms and has the potential to be developed as an agrochemical. Antibiotic-producing microorganisms have developed self-resistance mechanisms to protect themselves from autotoxicity. Antibiotic efflux is vital for such protection. Recently, we identified a resistance-nodulation-division (RND) efflux pump, LexABC, involved in self-resistance against myxin in L. antibioticus. Expression of its genes, lexABC, was induced by myxin and was positively regulated by the LysR family transcriptional regulator LexR. The molecular mechanisms, however, have not been clear. Here, LexR was found to bind to the lexABC promoter region to directly regulate expression. Moreover, myxin enhanced this binding. Molecular docking and surface plasmon resonance analysis showed that myxin bound LexR with valine and lysine residues at positions 146 (V146) and 195 (K195), respectively. Furthermore, mutation of K195 in vivo led to downregulation of the gene lexA. These results indicated that LexR sensed and bound with myxin, thereby directly activating the expression of the LexABC efflux pump and increasing L. antibioticus resistance against myxin. IMPORTANCE Antibiotic-producing bacteria exhibit various sophisticated mechanisms for self-protection against their own secondary metabolites. RND efflux pumps that eliminate antibiotics from cells are ubiquitous in Gram-negative bacteria. Myxin is a heterocyclic N-oxide phenazine with potent antimicrobial and antitumor activities produced by the soil bacterium L. antibioticus. The RND pump LexABC contributes to the self-resistance of L. antibioticus against myxin. Herein, we report a mechanism involving the LysR family regulator LexR that binds to myxin and directly activates the LexABC pump. Further study on self-resistance mechanisms could help the investigation of strategies to deal with increasing bacterial antibiotic resistance and enable the discovery of novel natural products with resistance genes as selective markers.

Modeling Antibiotic Concentrations in the Vicinity of Antibiotic-Producing Bacteria at the Micron Scale.

It is generally thought that antibiotics confer upon the producing bacteria the ability to inhibit or kill neighboring microorganisms, thereby providing the producer with a significant competitive advantage. Were this to be the case, the concentrations of emitted antibiotics in the vicinity of producing bacteria might be expected to fall within the ranges of MICs that are documented for a number of bacteria. Furthermore, antibiotic concentrations that bacteria are punctually or chronically exposed to in environments harboring antibiotic-producing bacteria might fall within the range of minimum selective concentrations (MSCs) that confer a fitness advantage to bacteria carrying acquired antibiotic resistance genes. There are, to our knowledge, no available in situ measured antibiotic concentrations in the biofilm environments that bacteria typically live in. The objective of the present study was to use a modeling approach to estimate the antibiotic concentrations that might accumulate in the vicinity of bacteria that are producing an antibiotic. Fick's law was used to model antibiotic diffusion using a series of key assumptions. The concentrations of antibiotics within a few microns of single producing cells could not reach MSC (8 to 16 μg/L) or MIC (500 μg/L) values, whereas the concentrations around aggregates of a thousand cells could reach these concentrations. The model outputs suggest that single cells could not produce an antibiotic at a rate sufficient to achieve a bioactive concentration in the vicinity, whereas a group of cells, each producing the antibiotic, could do so. IMPORTANCE It is generally assumed that a natural function of antibiotics is to provide their producers with a competitive advantage. If this were the case, sensitive organisms in proximity to producers would be exposed to inhibitory concentrations. The widespread detection of antibiotic resistance genes in pristine environments suggests that bacteria are indeed exposed to inhibitory antibiotic concentrations in the natural world. Here, a model using Fick's law was used to estimate potential antibiotic concentrations in the space surrounding producing cells at the micron scale. Key assumptions were that per-cell production rates drawn from the pharmaceutical manufacturing industry are applicable in situ, that production rates were constant, and that produced antibiotics are stable. The model outputs indicate that antibiotic concentrations in proximity to aggregates of a thousand cells can indeed be in the minimum inhibitory or minimum selective concentration range.

Evolution of genome fragility enables microbial division of labor.

Division of labor can evolve when social groups benefit from the functional specialization of its members. Recently, a novel means of coordinating the division of labor was found in the antibiotic-producing bacterium Streptomyces coelicolor, where specialized cells are generated through large-scale genomic re-organization. We investigate how the evolution of a genome architecture enables such mutation-driven division of labor, using a multiscale computational model of bacterial evolution. In this model, bacterial behavior-antibiotic production or replication-is determined by the structure and composition of their genome, which encodes antibiotics, growth-promoting genes, and fragile genomic loci that can induce chromosomal deletions. We find that a genomic organization evolves, which partitions growth-promoting genes and antibiotic-coding genes into distinct parts of the genome, separated by fragile genomic loci. Mutations caused by these fragile sites mostly delete growth-promoting genes, generating sterile, and antibiotic-producing mutants from weakly-producing progenitors, in agreement with experimental observations. This division of labor enhances the competition between colonies by promoting antibiotic diversity. These results show that genomic organization can co-evolve with genomic instabilities to enable reproductive division of labor.

Detection of microorganisms with antibacterial activities from different industrial wastes and GC-MS analysis of crude microbial extract.

Many soil microorganisms' i.e., bacteria and fungi produce secondary metabolites called antibiotics. These are used for the treatment of some of the bacterial, fungal and protozoal diseases of humans. There is a need for isolation of a broad spectrum of antibiotics from microorganisms due to the emergence of antibiotic resistance. In the present study two antibiotic producing bacteria Klebsiella pneumoniae and Bacillus cereus were isolated from pharmaceutical and poultry feed industry of Hattar, Haripur Pakistan. Total 10 waste samples were collected from different industries (Marble, Ghee, Soap, Mineral, Steel, Poultry Feed, Pharmaceutical, Qarshi, Cosmetic and Glass). Thirty-three bacterial strains were isolated from industrial wastes of these ten different industries. Fourteen out of thirty-three bacterial strains exhibited antimicrobial activities against at least one of the test microbes considered in this study including Escherchia coli, Staphylococcus aureus and Salmonella typhi. The bacteria were isolated by standard serial dilution spread plate technique. Morphological characterization of the isolates was done by Gram staining. Nine bacterial isolates out of fourteen were initially identified as B. cereus and five as K. pneumoniae through biochemical characterization. The antibacterial activities were tested by well diffusion method. Maximum number of antibiotic producing bacteria were isolated from pharmaceutical and poultry feed industry based on the results of primary screening, the most potential isolates S9, S19, S20, S22 and S23 were selected for secondary screening. The maximum activity against E. coli and S. aureus was recorded by bacterial isolate S19 i.e zones of inhibition of 6.5mm and 9mm while S20 showed 7.5mm and 6mm zones respectively. Molecular identification was carried out on the basis of 16S rRNA sequence analysis. Finally, the isolates were identified as B. cereus accession number LC538271and K. pneumoniae accession number MT078679. Analysis of bacterial extract S20 through GC-MS indicated the presence of 8 compounds of diverse nature and structure. Present study suggests that wastes of pharmaceutical and poultry feed industry may have antibiotic producing bacteria. These bacteria could be utilized for the production of antibiotics. B. cereus and K. pneumoniae isolated from wastes of poultry feed and pharmaceutical industries have the potential to produce antibiotics and could be used to control the microbial growth.

Screening and characterization of antibiotic producing bacteria from rhizospheric soil against fungal phytopathogens

In this study, antagonistic bacteria were isolated from rhizospheric soil collected from Himachal Pradesh (i.e., Solan and Hamirpur) and Punjab (i.e., Jalandhar and Pathankot). Sixty- eight bacteria were isolated and screened for antifungal activity against Botrytis oryzae, Aspergillus flavus, and Fusarium oxysporum. Three isolates, i.e., S7, S57, and S51, showed maximum inhibition for antifungal activity by using the agar streak method and were further selected for in vitro characterization. In vitro antifungal antibiotic study by using agar diffusion assay of isolates, i.e., S7, S57, and S51 at O.D. 2.0 showed maximum inhibition of 99% against Botyritis oryzae, Fusarium oxysporum, and Aspergillus flavus after seven days of incubation. Antibiotic assays using cell-free supernatant of antagonistic bacterial isolates, i.e., S7 and S57, showed complete inhibition at 10% against Botyritis oryzae and Fusarium oxysporum, whereas isolate S51 showed complete inhibition at 20% against Aspergillus flavus. The bacterial isolates were partially identified based on morphological and biochemical characteristics. The selected antagonistic bacterial isolates S7 and S57 appeared to be similar to Bacillus sp. and S51 to Actinomycete sp. Thus, the present study concludes that these bacterial isolates could serve as proficient biocontrol inoculants in the integrated management of soil-borne diseases in different crops under natural environmental conditions.

Activation of ChvG-ChvI regulon by cell wall stress confers resistance to β-lactam antibiotics and initiates surface spreading in Agrobacterium tumefaciens.

A core component of nearly all bacteria, the cell wall is an ideal target for broad spectrum antibiotics. Many bacteria have evolved strategies to sense and respond to antibiotics targeting cell wall synthesis, especially in the soil where antibiotic-producing bacteria compete with one another. Here we show that cell wall stress caused by both chemical and genetic inhibition of the essential, bifunctional penicillin-binding protein PBP1a prevents microcolony formation and activates the canonical host-invasion two-component system ChvG-ChvI in Agrobacterium tumefaciens. Using RNA-seq, we show that depletion of PBP1a for 6 hours results in a downregulation in transcription of flagellum-dependent motility genes and an upregulation in transcription of type VI secretion and succinoglycan biosynthesis genes, a hallmark of the ChvG-ChvI regulon. Depletion of PBP1a for 16 hours, results in differential expression of many additional genes and may promote a stress response, resembling those of sigma factors in other bacteria. Remarkably, the overproduction of succinoglycan causes cell spreading and deletion of the succinoglycan biosynthesis gene exoA restores microcolony formation. Treatment with cefsulodin phenocopies depletion of PBP1a and we correspondingly find that chvG and chvI mutants are hypersensitive to cefsulodin. This hypersensitivity only occurs in response to treatment with β-lactam antibiotics, suggesting that the ChvG-ChvI pathway may play a key role in resistance to antibiotics targeting cell wall synthesis. Finally, we provide evidence that ChvG-ChvI likely has a conserved role in conferring resistance to cell wall stress within the Alphaproteobacteria that is independent of the ChvG-ChvI repressor ExoR.

Isolation and identification of promising antibiotic-producing bacteria

Abstract Multiple stresses in waste dumpsite soils can drive antibiotic production as one of the strategies for survival. Bacteria are the most prolific producers of antibiotics. This study investigated the antibiotic production potential of bacteria isolated from Bahir Dar city municipal solid waste dumpsite (MSWDS). Bacteria were isolated from soil collected from the dumpsite on starch casein or nutrient agar. The isolates were carefully screened for antimicrobial activity against six pathogenic bacterial test strains. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were also determined from cell-free metabolites of the most promising isolates. Isolates showing antimicrobial activity were identified using cultural and biochemical methods. A total of 143 distinctive colonies were obtained and tentatively identified to 13 bacterial genera. Twenty-six (18.18%) of the isolates (six Bacillus and 20 actinobacteria related) demonstrated antimicrobial activities at least against one of the tested bacterial strains. These isolates were related to two actinobacterial and 11 other bacterial genera. Seven out of 26 isolates showed a broad-spectrum of antibiotic activities. Two isolates, which showed a wide spectrum, were selected for the MIC and MBC tests against Escherichia coli and Staphylococcus aureus. The MIC and MBC of the isolates were recorded to be 250–500 µg/mL against the test strains. Bahir Dar city MSWDS contained a high incidence of antibiotic-producing bacteria. Strain level identification of the isolates and detailed characterization of the metabolites will give a good insight into the antimicrobial production potential in the waste dumpsite.

Microbial infection risk predicts antimicrobial potential of avian symbionts.

Symbiotic bacteria on animal hosts can prevent pathogenic bacterial infections by several mechanisms. Among them, symbiotic bacteria can indirectly enhance host's immune responses or, directly, produce antimicrobial substances against pathogens. Due to differences in life-style, different host species are under different risks of microbial infections. Consequently, if symbiotic bacteria are somewhat selected by genetically determined host characteristics, we would expect the antimicrobial properties of bacterial symbionts to vary among host species and to be distributed according to risk of infection. Here we have tested this hypothesis by measuring the antimicrobial ability of the bacterial strains isolated from the uropygial-gland skin of 19 bird species differing in nesting habits, and, therefore, in risk of microbial infection. In accordance with our predictions, intensity and range of antimicrobial effects against the indicator strains assayed varied among bird species, with hole-and open-nesters showing the highest and the lowest values, respectively. Since it is broadly accepted that hole-nesters have higher risks of microbial infection than open nesters, our results suggest that the risk of infection is a strong driver of natural selection to enhance immunocompetence of animals through selecting for antibiotic-producing symbionts. Future research should focus on characterizing symbiotic bacterial communities and detecting coevolutionary processes with particular antibiotic-producing bacteria within-host species.

Exploration of Antibiotics-Producing Endophytic Bacteria Isolates from Betel Leaves in Jambi City Forest Park.

<b>Background and Objective:</b> Sources of antibiotics that are cheap and easy to obtain are by exploiting endophytic microbes from betel plants because betel plant extracts are known to produce anti-microbial compounds. This research aimed to obtain isolates of antibiotic producer endophilic bacteria from betel leaves in Jambi city forest park. <b>Materials and Methods:</b> This research consists of several stages, sterilization of the collected betel leaf surface, isolation and purification of endophytic bacterial isolates, screening of antibiotic-producing bacteria and characterization of endophytic bacteria. <b>Results:</b> There were 3 types of betel plants found in the area, namely: <i>Piper betle</i> L. (green betel), <i>Piper crocatum</i> Ruiz and Pav (red betel) and <i>Piper aduncum</i> L. (forest betel). In red betel leaves, 9 types of endophytic bacterial isolates were obtained, while only 1 isolate was found in each green betel and forest betel leaf. Of these 11 isolates, 9 of them produced antibiotics. However, only 6 isolates were potential since they had a halo zone bigger than 10 mm for <i>E. coli</i> (gram-negative) and <i>S. aureus</i> (gram-positive). Among these 6 isolates, 5 isolates were from red leaves with isolate codes of BESKJ-m2, BESHKJ-m3, BESHKJ-m4, BESHKJ-m5, BESHKJ-m6 and 1 isolate from forest betel leaves with code of BESHKJ-s1. <b>Conclusion:</b> From the control positive test using chloramphenicol, it was known that the endophilic bacteria had a broad spectrum. The bacterial colonies were white and had an elevation on the surface of the media with flat to irregular margins. The catalase and Gram stain tests showed that the bacteria were Gram-positive.

Complete genome sequencing and in silico genome mining reveal the promising metabolic potential in Streptomyces strain CS-7.

Gram-positive Streptomyces bacteria can produce valuable secondary metabolites. Streptomyces genomes include huge unknown silent natural product (NP) biosynthetic gene clusters (BGCs), making them a potential drug discovery repository. To collect antibiotic-producing bacteria from unexplored areas, we identified Streptomyces sp. CS-7 from mountain soil samples in Changsha, P.R. China, which showed strong antibacterial activity. Complete genome sequencing and prediction in silico revealed that its 8.4 Mbp genome contains a total of 36 BGCs for NPs. We purified two important antibiotics from this strain, which were structurally elucidated to be mayamycin and mayamycin B active against Staphylococcus aureus. We identified functionally a BGC for the biosynthesis of these two compounds by BGC direct cloning and heterologous expression in Streptomyces albus. The data here supported this Streptomyces species, especially from unexplored habitats, having a high potential for new NPs.