Culturable Endophytic Bacteria Research Articles

Whole-genome sequencing of four culturable endophytic bacteria from German hardneck garlic cloves (Allium sativum L.).

We present the whole-genome sequence of four bacterial endophytes associated with German hardneck garlic cloves (Allium sativum L.). Among them, Agrobacterium fabrum and Pantoea agglomerans are associated with plant protection, while Rahnella perminowiae and Stenotrophomonas lactitubi are pathogens. These data will facilitate the identification of genes to improve garlic.

Proteobacterial dominance in endophytic bacterial diversity in switchgrass growing under nitrogen range and effect on plant growth

Switchgrass (Panicum virgatum L.) is native to North America and cultivated as a forage and bioenergy crop. Inorganic fertilizers enhance biomass production, increase production costs, and pollute the environment. Switchgrass cultivation using an eco-friendly approach might be achieved by inoculation with beneficial microbes. Therefore, the diversity of cultivable endophytic bacteria from roots and shoots of switchgrass growing under a nitrogen regime was studied. The potential of bacteria for plant growth promotion (PGP) was tested under in vitro conditions. A total of 216 bacterial isolates obtained belonged to four phyla and 33 genera, and most isolates were obtained from plants growing under no (0 kg/ha) or low nitrogen (90 kg/ha) input, rather than higher N (180 kg/ha). Higher numbers of isolates belonged to the phylum Proteobacteria, and genus-wise representation showed the dominance of Pseudomonas, Enterobacter, and rhizobia. Bacterial isolates were tested for PGP properties, e.g. phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, Indole Acetic Acid (IAA) production, and nitrogen fixation. Many isolates were positive for one or more PGP properties. In in vitro analysis, selected bacterial isolates were inoculated in two commercial switchgrass cultivars and a showed cultivar-specific response. PGP isolates can be used for pot or field trials and eventually for the sustainable cultivation of switchgrass.

Culturable Diversity and Biological Properties of Bacterial Endophytes Associated with the Medicinal Plants of Vernonia anthelmintica (L.) Willd

As one of the important traditional medicinal plants listed in the Chinese pharmacopoeia, Vernonia anthelmintica (L.) Willd has been shown to possess various biological activities. In this study, we characterized culturable endophytic bacteria associated with the medicinal plant V. anthelmintica collected from Hotan within the Xinjiang autonomous region of China. Bacterial endophytes were identified via 16S rRNA gene sequence analysis and compared to similar sequences from the GenBank. Isolated strains exhibited 99.08–100% similarity to Bacillus haynesii XJB-5, Bacillus proteolyticus XJB-16, Bacillus halotolerans XJB-35, Bacillus safensis XJB-71, Pseudomonas punonensis XJB-7, Lysinibacillus fusiformis XJB-17, Streptococcus lutetiensis XJB-66, Leclercia adecarboxylata XJB-12, Paenibacillus alvei XJB-14, and Pantoea agglomerans XJB-62. The ethyl acetate extracts of the bacterial endophytes demonstrated various pharmacological properties, such as antimicrobial, cytotoxic, antidiabetic, and antioxidant activity, according to a melanin content assay and have shown tyrosinase activity in murine B16 cells. A crude extract of B. halotolerans XJB-35 displayed more powerful biological activities than other bacterial endophytes; therefore, this strain was studied further in order to select the optimized parameters for enhancing the synthesis of bioactive compounds. The optimal culture medium was found to be nutrient broth (NB) medium, using peptone as its carbon source and yeast extract as its nitrogen source. A 24 h incubation time produced the optimal conditions for the maximum growth of B. halotolerans XJB-35 and the production of bioactive compounds. Moreover, we investigated the volatile chemical component of the dichloromethane fraction using GC-MS analysis. Our findings provide valuable information regarding the synthesize of bioactive natural products by B. halotolerans XJB-35 for use by the medicinal and pharmaceutical industries.

Ultra-high-performance liquid chromatography-tandem high-resolution elevated mass spectrometry profiling of anti-methicillin-resistant Staphylococcus aureus metabolites from the endophytic bacteria collected from the weeds of a previous dumpsite

The culturable endophytic bacteria from the weeds Cleome rutidosperma of the family Cleomaceae and Digitaria sanguinalis of the family Poaceae obtained from a previous dumpsite in Pampanga, Philippines have been assessed for their anti-methicillin-resistant Staphylococcus aureus (MRSA) activity, and the analytes with such activity should be identified. However, due to the limited amounts collected from the isolation process, 1.8 mg yield of compound 1 from the endophyte of C. rutidosperma and 1.2 mg of a mixture from the endophyte of D. sanguinalis were selected for LC-MSE analysis. The production of compounds from the culturable endophytic bacteria Pseudomonas aeruginosa— determined by gene-sequencing, an untargeted and data-independent analysis (DIA) by ultra-high performance liquid chromatography-high resolution-elevated energy mass spectrometry (UHPLC-HR-MSE) technique was employed to profile the metabolites present in the two high-performance liquid chromatography (HPLC) fractions. The analytes present from P. aeruginosa detected by UHPLC-HR-MSE isolated from C. rutidosperma was phenazine-1-carboxylic acid (1), and for D. sanguinalis were chamigrenal (2), dialkyl resorcinol (3), and a pyoverdine elicitor (4). This study proves that UHPLC-HR-MSE could identify the anti-MRSA constituents in P. aeruginosa from commensal weeds C. rutidosperma and D. sanguinalis. The UHPLC-HR-MSE could help strengthen metabolomics antibacterial research and its related applications from a future perspective. Application of metabolomics research using UHPLC-HR-MSE could enhance the rehabilitation of dumpsites by the microbial community present.

Biodiversity of Endophytic Microbes in Diverse Tea Chrysanthemum Cultivars and Their Potential Promoting Effects on Plant Growth and Quality.

The endophytic microbiomes significantly differed across tea chrysanthemum cultivars and organs (stems and leaves). The most abundant endophytic bacterial genera were Pseudomonas, Masillia, and Enterobacter in the leaves and Sphingomonas and Curtobacterium in the stems of the five cultivars. Meanwhile, the most abundant endophytic fungal genera in the leaves and stems of the five tea chrysanthemums were Alternaria, Cladosporium, and Sporobolomyces. Specifically, Rhodotorula was dominant in the leaves of 'Jinsi huangjv' and Paraphoma was dominant in the stems of 'Jinsi huangjv'. In all cultivars, the diversity and richness of endophytic bacteria were higher in leaves than in stems (p < 0.05). The highest diversity and richness of endophytic bacteria were recorded in 'Chujv', followed by 'Jinsi huangjv', 'Fubai jv', 'Nannong jinjv', and 'Hangbai jv'. Meanwhile, endophytic fungi were less pronounced. Twenty-seven and 15 cultivable endophytic bacteria and fungi were isolated, four isolated endophytic bacteria, namely, CJY1 (Bacillus oryzaecorticis), CY2 (Pseudomonas psychrotolerans), JSJ7, and JSJ17 (Enterobacter cloacae) showed higher indole acetic acid production ability. Further field studies indicated that inoculation of these four endophytic bacteria not only promoted plant growth and yield but also increased total flavonoids, chlorogenic acid, luteolin, and 3,5-dicoffeylquinic acid levels in the dry flowers of tea chrysanthemums.

Isolation of Culturable Endophytic Bacteria from the Roots of Aloe Vera L. (Aloe Barbadensis Miller) and Their Application in Phytodegradation of Xenobiotics

Isolation of Culturable Endophytic Bacteria from the Roots of Aloe Vera L. (Aloe Barbadensis Miller) and Their Application in Phytodegradation of Xenobiotics

16S rRNA gene‐based identification and plant growth‐promoting potential of cultivable endophytic bacteria

AbstractEndophytic bacteria play essential roles in plant growth and fitness through nitrogen fixation, nutrient solubilization, and phytohormone production. However, the plant growth‐promoting (PGP) potential of endophytic microorganisms inhabiting vegetables is underexplored. Thus, this study investigated the endophytic bacteria of vegetable crops for their PGP properties using the culture‐dependent technique. Recovered isolates were identified by sequencing the partial 16S rRNA gene using Sanger sequencing. The isolated endophytic bacteria belonged to 15 genera and 39 different species. Bacillus, Enterobacter, Pantoea, and Pseudomonas were the predominant genera and had high phosphate solubilization and siderophore production potential. The isolates differentially produced indole‐3‐acetic acid and ammonium in the range 0.14–44.48 μg mL–1 and 0.77–93.24 mg L–1, respectively. Pseudomonas azotoformans, Stenotrophomonas maltophilia, and Serratia liquefaciens showed a high level of siderophore production, which was not significantly (p &gt; 0.05) different across the plant and organ types. More than 21% of endophytes could produce gelatinase, protease, amylase, and cellulase, contributing to their diverse ecosystem functions. Bacterial density and species composition varied across the vegetable species, organs, and farm locations but were higher in the stems compared with other organs. However, the vegetable organ had no significant (p &gt; 0.05) influence on the bacterial population density, except for the interaction of plant species and organs. Overall, this study provides basic knowledge about the cultivable endophytic bacterial community of vegetables and reveals diverse endophytic bacteria useful in bioinoculant formulations for improving crop productivity.

Characterization and Antagonistic Effect of Culturable Apple-Phyllosphere Endophytic Bacteria from the Cold Plateau in Yunnan, China

The endophytic bacteria in apple leaves from apple-producing areas of Yunnan, China were isolated and identified on the basis of bacterial colony morphology and nucleotide sequences of 16S rRNA and rpoB genes. The endophytic bacterial isolates with nitrogen, phosphorus, and potassium utilization abilities were screened by culturing on functional media. A total of 5709 isolates of culturable endophytic bacteria (CEB) were isolated from 30 apple leaf samples collected from different regions. A total of 39 CEB representative isolates were identified as Bacillus velezensis, B. subtilis, B. licheniformis, B. safensis, B. pumilus, and Priestia megaterium. Among them, B. velezensis and B. subtilis were the main CEB, accounting for 55.00% and 34.37%, respectively, which exhibited potential inhibition on not only the main apple disease pathogens of Alternaria alternata, Valsa mali, Fusarium oxysporum, and Rosellinia necatrix, but also some important and uncontrollable phytopathogens, including F. oxysporum f. sp. cubense that causes banana Fusarium wilt, and Phytophthora nicotianae that causes tobacco black shank. Among these isolated endophytic bacteria species, a total of 10 strains, including b3, b4, b16, b17, b20, and b23 of B. subtilis, b7, b24, and b28 of B. licheniformis, and b38 of B. velezensis, can fix nitrogen; 8 strains, including b7 and b28 of B. licheniformis, b5, b10, and b23 of B. subtilis, b8 of B. safensis, and b6 of Priestia megaterium, could dissolve inorganic phosphorus; 11 strains, including b9, b12, b14, b30, b34, and b43 of B. velezensis, b6 of Priestia megaterium, and b17, b18, b20, and b26 of B. subtilis, could degrade organic phosphorus; and 5 strains, including b4, b5, and b26 of B. subtilis, and b7 and b28 of B. licheniformis could dissolve potassium. These strains are valuable resources of endophytic bacteria that have adapted to the ecological environment of the Cold Plateau apple-production area and could be used as plant disease biocontrol agents and biofertilizers of crops. The culturable phyllosphere endophytes in apple leaves relate to geographic locations, apple varieties, and environment, providing the basis to explain the mechanisms underlying the establishment of apple endophyte diversity and may help to devise apple disease management strategies.

Culture on Nutritive Media and Characterization of Some Endophytic Bacteria Isolated from the Roots and Leaves of Mangrove Plants: Avicennia germinans, Acrostichum aureum and Rhizophora mangle

Aim: The aim of this study was to isolate and characterize the culturable endophytic bacteria from the roots and leaves of three different mangrove plants found growing in same environment.&#x0D; Study Design: This study employs experimental design, statistical analysis of the data and interpretation.&#x0D; Place of Study: The roots and leaves of three mangrove plants; Rhizophora mangle, Avicennia germinans and Acrostichum aureum were gotten from a waterfront location in old Port Harcourt township of Rivers State, situated at Longitude 40 45’5.18’’N and Latitude 70 0’58.35” E.&#x0D; Methodology: Using standard Microbiological techniques, the roots and leaves were treated and endophytic bacteria isolated and subjected to morphological and biochemical tests.&#x0D; Results: From the roots, the hydrocarbon utilizing bacteria counts ranged from 7.0x103cfu/g – 1.6x104cfu/g, while the that of the leaves ranged from 3.0 x105cfu/g – 8.0 x105cfu/g. The nitrogen fixing bacteria counts for roots ranged from 4.5 x103cfu/g – 1.0 x104cfu/g and that of the leaves ranged from 3.0 x105cfu/g – 6.0 x105cfu/g. Nitrifying bacteria counts for the roots ranged from 5.0x103cfu/g – 7.0x103cfu/g, while the counts from the leaves ranged from 3.5 x 105cfu/g - 5.0 x105cfu/g. Out of the 24 isolates, 14 were from the roots, while 10 were from the leaves. Percentage of occurrence of the isolates was in this order Bacillus sp 33% &gt; Staphylococcus sp 21%&gt; Klebsiella sp 13%&gt; Pseudomonas sp 9%&gt; Micrococcus sp 8%&gt; Nitrobacter sp 8%&gt; Nitrosomonas sp 4%&gt; Azotobacter sp 4%. This reveals that Bacillus sp occurred most in the plant samples. The result also revealed that the Red Mangrove Roots had the highest number of organisms. The endophytic bacteria isolated were further subjected to morphological and biochemical identification and they were identified as: Pseudomonas sp, Bacillus sp, Staphylococcus sp, Micrococcus sp, Klebsiella sp, Azotobacter sp, Nitrobacter sp. and Nitrosomonas sp. Five of the isolates showed a high potential to degrade crude oil in the following order Pseudomonas sp (H2) &gt; Bacillus sp (BA) &gt; Klebsiella sp (SB)&gt; Bacillus sp (TG) &gt; Pseudomonas sp (H1).&#x0D; Conclusion: From the results, the mangrove roots and leaves contained high numbers of active indigenous bacteria most of which are known to use up crude oil as their carbon source. The mangrove roots had higher number of endopyhtic bacteria than the leaves.

Culturable Endophytes Associated with Soybean Seeds and Their Potential for Suppressing Seed-Borne Pathogens.

Seed-borne pathogens in crops reduce the seed germination rate and hamper seedling growth, leading to significant yield loss. Due to the growing concerns about environmental damage and the development of resistance to agrochemicals among pathogen populations, there is a strong demand for eco-friendly alternatives to synthetic chemicals in agriculture. It has been well established during the last few decades that plant seeds harbor diverse microbes, some of which are vertically transmitted and important for plant health and productivity. In this study, we isolated culturable endophytic bacteria and fungi from soybean seeds and evaluated their antagonistic activities against common bacterial and fungal seed-borne pathogens of soybean. A total of 87 bacterial isolates and 66 fungal isolates were obtained. Sequencing of 16S rDNA and internal transcribed spacer amplicon showed that these isolates correspond to 30 and 15 different species of bacteria and fungi, respectively. Our antibacterial and antifungal activity assay showed that four fungal species and nine bacterial species have the potential to suppress the growth of at least one seed-borne pathogen tested in the study. Among them, Pseudomonas koreensis appears to have strong antagonistic activities across all the pathogens. Our collection of soybean seed endophytes would be a valuable resource not only for studying biology and ecology of seed endophytes but also for practical deployment of seed endophytes toward crop protection.

Chickpea (Cicer arietinum L.) Seeds as a Reservoir of Endophytic Plant Growth-Promoting Bacteria.

The seed microbiome, the primary source of inoculum for plants, may play an important role in plant growth, health and productivity. However, the structure and function of chickpea seed endophytes are poorly characterized. Bacteria with beneficial characteristics can be selected by the plant and transmitted vertically via the seed to benefit the next generation. Studying the diversity and multifunctionality of seed microbial communities can provide innovative opportunities in the field of plant-microbe interaction. This study aimed to isolate, identify and characterize culturable endophytic bacteria from chickpea (Cicer arietinum L.) seeds. Phylogenetic analysis based on 16S rDNA showed that the endophytic bacteria belong to the genera Mesorhizobium, Burkholderia, Bacillus, Priestia, Paenibacillus, Alcaligenes, Acinetobacter, Rahnella, Enterobacter, Tsukamurella, and Microbacterium. The most frequently observed genus was Bacillus; however, rhizobia typically associated with chickpea roots were also found, which is a novel finding of this study. Siderophore production and phosphorus solubilization were the most widespread plant growth-promoting features, while hydrogen cyanide production was relatively rare among the isolates. Most of the isolates possess two or more plant growth-promoting features; however, only Bacillus thuringiensis Y2B, a well-known entomopathogenic bacteria, exhibited the presence of all plant growth-promoting traits evaluated. Results suggest that endophytic bacteria such as Bacillus, Mesorhizobium, and Burkholderia may be vertically transferred from inoculated plants to seeds to benefit the next generation.

Tailored Media Are Key to Unlocking the Diversity of Endophytic Bacteria in Distinct Compartments of Germinating Seeds.

ABSTRACTSeeds offer an internal microbial niche, termed the endosphere, colonized by communities of endophytic bacteria. To elucidate the functions of seed endophytes during germination and early plant growth, studies with culturable isolates are essential. Conventional growth media favor few fast-growing taxa, while micro organisms with restricted nutrient requirements are usually outcompeted prior to isolation. Consequently, current knowledge of the interaction between seeds and their endophytes remains limited to only few bacterial taxa, despite a “black box” of unculturable isolates colonizing the endosphere. Here, we designed various solid media to mimic the endosphere of germinating soybean (Glycine max L.) seeds and assessed their effect on the diversity of culturable endophytic bacteria. The embryonic axis (i.e., the future plant) possessed higher richness and harbored more unique genera (i.e., Brevundimonas, Methylobacterium, Microbacterium, Pseudoclavibacter, and Rathayibacter) than cotyledons (i.e., seed storage organs). Overall, media containing germinating and ground seeds enabled culturing and isolation of the broadest diversity of endophytic bacteria, viewed through the molecular identification of 246 isolates. The use of multiple tailored media helped uncover trophic adaptation of the core taxa. Furthermore, comparison of seeds from four lots of distinct cultivars and origin revealed few overlapping taxa, indicating that the parental environment, including soil and fertilization regime, influenced seed endophytic diversity. Extended diversity of native seed endophytic bacteria revealed the functional relevance of unique Arthrobacter, Bacillus, and Curtobacterium strains to seed germination under salt stress, exemplifying the importance of enhanced culturing approaches to elucidate the role of microbiota in seed germination.IMPORTANCE Plant growth-promoting endophytic isolates that appear to advance seed germination are often obtained from plant niches other than the seed endosphere. Isolating pure cultures of native endophytes from seeds during germination is crucial to investigate their function during early plant growth. Here, the diversity of endophytic bacteria isolated from seeds during soybean germination was enhanced by combining media tailored to the nutritional composition of the seed endosphere, including pregerminated seeds themselves. Our results show that isolation from distinct soybean seed compartments affected such diversity, with the embryonic axis harboring more unique taxa while displaying higher endophytic richness. Furthermore, using pools of seeds from separate lots, each corresponding to a certain cultivar and field site, supported isolation of further unique strains that often unveiled substantial effects on germination performance. Such findings are relevant to assist studies on the interactions between seeds and their native endophytic bacteria.

Diversity, Antimicrobial Activity, and Antibiotic Susceptibility Pattern of Endophytic Bacteria Sourced From Cordia dichotoma L.

Endophytic bacteria isolated from medicinal plants are crucial for the production of antimicrobial agents since they are capable of possessing bioactive compounds with diverse structures and activities. Cordia dichotoma, a plant of medicinal importance native to the Jammu region of India, was selected for the isolation and characterization of culturable endophytic bacteria and evaluation of their antimicrobial activities. Standardized surface sterilization methods were employed to isolate thirty-three phenotypically distinguishable endophytic bacteria from the root, stem, and leaf parts of the plant. Shannon Wiener diversity index clearly divulged diverse endophytes in roots (0.85), stem (0.61), and leaf (0.54) tissues. Physio-biochemical features of the isolates differentiated the distinct variations in their carbohydrate utilization profile and NaCl tolerance. The endophytes produced an array of enzymes, namely, catalase, oxidase, amylase, cellulase, nitrate reductase, and lipase. The bacterial isolates belong to the genera Bacillus, Pseudomonas, Paenibacillus, Acidomonas, Streptococcus, Ralstonia, Micrococcus, Staphylococcus, and Alcalignes predominantly. However, the antibiotic susceptibility pattern indicated that the isolates were mostly sensitive to erythromycin and streptomycin, while they were resistant to rifampicin, amoxicillin, and bacitracin. Interestingly, majority of the bacterial endophytes of C. dichotoma showed antimicrobial activity against Bacillus subtilis followed by Klebsiella pneumoniae. The 16S rRNA sequence of Bacillus thuringiensis has been deposited in the NCBI GenBank database under accession number OM320575. The major compounds of the crude extract derived from endophytic B. thuringiensis OM320575, according to the metabolic profile examination by GC-MS, are dibutyl phthalate, eicosane, tetrapentacontane, heneicosane, and hexadecane, which possessed antibacterial activities. In conclusion, results indicated the potential of C. dichotoma to host a plethora of bacterial endophytes that produce therapeutic bioactive metabolites.

A comprehensive characterization of culturable endophytic bacteria of Paris polyphylla and their potential role in microalgal growth in co-culture

Expanding endophytes of endangered medicinal plant Paris polyphylla can provide a means to study endo-symbiotic relationships with emphasis on different traits such as plant growth promotion (PGP), host-defence mechanism, and secondary metabolites production. As in many instances, endophytic isolates selected based on few traits fail when they are further screened for their direct role in plants. Therefore, in this study, we aimed to conduct comprehensive analyses on the under-explored endophytic bacterial community of P. polyphylla from the Himalayan mountains. Culture-dependent method was adapted to isolate under-explored endophytic bacterial community from the rhizomes of P. polyphylla. Isolates were identified using 16S rRNA gene sequencing and screened for different characteristics such as ability to grow in different temperatures, pH, and NaCl concentration, siderophore production, phosphate solubilisation, and plant cell wall-degrading enzymes production. Key genes such as sfp, ituD, and genes encoding for NRPS, and PKS clusters involved in particular traits were identified. A total of 186 endophytic isolates were characterized, and assigned to 4 major phyla Firmicutes, Gammaproteobacteria, Alphaproteobacteria, and Actinobacteria. The stringent methodology identified 7.52% and 2.15% of the isolates as siderophore producers and phosphate solubilisers respectively. Draft genome of the potential PGP endophyte Bacillus paralicheniformis PPE102 was obtained and investigated for various traits related to plant-microbe interactions. Co-culture experiments showed that PPE102 induced growth and had a positive impact on the biochemical content of photosynthetic microalga Micractinium sp. GA001. This debut attempt characterized exclusive collection of endophytic bacteria from P. polyphylla. This isolated community can be further explored for unique, and commercially-important biological compounds.

The diversity of bacterial endophytes from Iris pseudacorus L. and their plant beneficial traits

This study reports the diversity of cultivable endophytic bacteria associated with yellow iris (Iris pseudacorus L.) by using 16S rRNA gene analysis and their plant beneficial traits. The 16S rRNA sequence similarities of endophytic bacteria isolated from the leaves and roots of yellow iris showed that the isolates belonged to the genera Staphylococcus, Streptomyces, Variovorax, Pantoea, Paenibacillus, Bacillus, Janthinobacterium, Enterobacter, Brevibacterium, Agrobacterium, Rhizobium, Xanthomonas translucens, and Pseudomonas. The endophytic bacteria Pseudomonas gessardii HRT18, Brevibacterium frigoritolerans HRT8, Streptomyces atratus HRT13, and Bacillus toyonensis HST13 exhibited antimicrobial activity against five plant pathogenic fungi Fusarium, Rhizoctonia, Botrytis, Pythium, and Alternaria. They also demonstrated the capability to produce chitinase, protease, glucanase, lipase, HCN, and indole-3-acetic acid (IAA). Thirteen isolates (46%) produced IAA, and the most active IAA producers were Bacillus cereus, Agrobacterium tumefaciens, Agrobacterium vitis, Bacillus megaterium, and Bacillus aryabhattai. The IAA producing bacterial isolates stimulated root and shoot growth of garden cress. Our findings suggest that medicinal plants could be a promising source for isolating plant-beneficial bacteria that can be used to enhance the growth and protect plants against soil-borne pathogens.

Preliminary estimates of the number and diversity of the culturable endophytic bacteria from Deschampsia antarctica and Colobanthus quitensis

Endophytes are able to promote the plant's growth and are essential for their hosts to overcome biotic and abiotic stress. Plant-promoting capacities of these microorganisms can be crucial for Antarctic plants. The aim of the study was to estimate the number and diversity of culturable endophytic microorganisms from Deschampsia antarctica and Colobanthus quitensis growing in different localities of the West Antarctic Peninsula. Methods. Serial dilutions of the surface-sterilized plant biomass were inoculated on the CASO (Merk, USA) and R2A (Merk, USA) media and cultured at room temperature for a week. Number of colonies and their morphotypes were estimated. Results. The number of colony-forming units in the aboveground part and roots of D. antarctica was 4×106 ±2×106 and 7×106 ±2×106 per g of biomass, respectively. The colony forming units CFU number in the aboveground part of C. quitensis was 3×106±1×106 per g of biomass. The highest number of CFU was in the roots of D. antarctica from Galindez Island on both media (n×107). The highest CFU number in C. quitensis was in plants from Deception Island on nutrient-poor (7×106) and -rich (1×107) media. The lowest value was found for C. quitensis from Cape Pérez (7×103 on R2A and 1×104 on CASO). There was no significant difference in the number of CFU grown on nutrient-poor and nutrient-rich medium, but the morphology of the CFU varied on the two media. 112 pure cultures of endophytes were isolated. The vast majority (78%) of the isolates were gram-negative rods. The number of cultured endophytes of Antarctic vascular plans varied across the samples, which can be affected both by the features of the individual plants and the ecology of sites where they grow. Bacterial communities did not significantly vary in number depending on the medium but did somewhat differ in morphology. A collection of 112 endophyte isolates was developed, which is important to study their genetic and physiological traits and mechanisms of plant-bacteria interaction. Conclusions. Isolation of the endophytic microorganisms is important to study their genetic and physiological traits and mechanisms of plant-bacteria interaction.Keywords: Antarctic hairgrass, Antarctic pearlwort, maritime Antarctica, symbionts of plants

Diversity and Plant Growth-Promoting Ability of Endophytic, Halotolerant Bacteria Associated with Tetragonia tetragonioides (Pall.) Kuntze.

The diversity of salt-tolerant cultivable endophytic bacteria associated with the halophyte New Zealand spinach (Tetragonia tetragonioides (Pall.) Kuntze) was studied, and their plant beneficial properties were evaluated. The bacteria isolated from leaves and roots belonged to Agrobacterium, Stenotrophomonas, Bacillus, Brevibacterium, Pseudomonas, Streptomyces, Pseudarthrobacter, Raoultella, Curtobacterium, and Pantoea. Isolates exhibited plant growth-promoting traits, including the production of a phytohormone (indole 3-acetic-acid), cell wall degrading enzymes, and hydrogen cyanide production. Furthermore, antifungal activity against the plant pathogenic fungi Fusarium solani, F. oxysporum, and Verticillium dahliae was detected. Ten out of twenty bacterial isolates were able to synthesize ACC deaminase, which plays a vital role in decreasing ethylene levels in plants. Regardless of the origin of isolated bacteria, root or leaf tissue, they stimulated plant root and shoot growth under 200 mM NaCl conditions. Our study suggests that halophytes such as New Zealand spinach are a promising source for isolating halotolerant plant-beneficial bacteria, which can be considered as potentially efficient biofertilizers in the bioremediation of salt-affected soils.

Cultivable Endophytic Bacteria in Seeds of Dongxiang Wild Rice and Their Role in Plant-Growth Promotion

Dongxiang wild rice (Oryza rufipogon Griff.) germplasm is a precious resource for the improvement of agronomic traits in rice. Rice seeds also harbor a diverse endophytic bacterial community, and their interactions with their hosts and each other can influence plant growth and adaptability. Here, we investigated the community composition of cultivable endophytic bacteria obtained from the surface-sterilized seeds of Dongxiang wild rice and screened them for plant growth-promoting traits. Phylogenetic analysis of 16S rRNA gene sequences indicated that the 47 isolates were affiliated with five classes and 13 discrete genera, and Bacillus and Microbacterium predominated. Evaluations of plant growth promoting (PGP) traits showed that 45 endophytic bacteria isolates produced between 3.37 and 90.11 μg mL−1 of Indole-3-acetic acid (IAA), with the highest yield of 90.11 μg mL−1 (Fse28). Further, 37 of the isolates were able to solubilize mineral phosphate, while 28 other isolates had the ability of N2-fixation, 17 isolates possessed 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity with the highest yield of 20.72 μmol mg−1 protein h−1 (Fse35), and 17 isolates were also able to produce siderophores. The two strains Fse28 and Fse35 had multiple PGP traits that significantly improved the agronomic traits (root length, shoot length, dry matter, and chlorophyll content) of cultivated rice seedlings. Our results illustrate the rich diversity of seed endophytic bacteria in Dongxiang wild rice and their potential for developing novel efficient bioinoculants to enhance soil fertility and favor seedling growth.

Influence of tissue and geographic locality on culturable endophytic bacteria of Atractylodes macrocephala.

The endophytic bacterial community and their diversity are closely related to the host's growth and development. This paper explores the culturable endophytic bacteria in the stems, leaves, roots and rhizomes of Atractylodes macrocephala (AM) of four localities (Yuqian, Wenxian, Pan'an and Pingjiang) and the potential correlation between the bacteria and plant bioactive compounds. A total of 118 endophytic bacteria belonging to 3 phyla, 5 classes, 11 orders, 26 families and 48 genera were isolated and identified from the four AM tissues. Among them, Bacillus was the dominant genus. In AM, the tissue type and locality influenced the endophytic bacterial community. Approximately 29.7 and 28.8% of the endophytic bacteria exhibited tissue specificity and geographic specificity, respectively. Furthermore, high-performance liquid chromatography revealed that the sesquiterpenoid (atractylenolide I, atractylenolide Ⅱ and atractylon) content was more in the rhizomes of Wenxian than in those of Pingjiang, Yuqian and Pan'an. The multiple linear regression was used to screen the bacterial strains related to the bioactive compounds of AM. The relative frequency of Microbacterium positively correlated with atractylenolide I and atractylon content in AM but negatively correlated with atractylenolide Ⅱ content. The study also provides a theoretical framework for future research on endophytic bacteria as alternative sources of secondary plant metabolites.

Plant growth-promoting abilities and community structure of culturable endophytic bacteria from the fruit of an invasive plant Xanthium italicum.

Diversity of endophytic bacterial communities of capsular fruit, upper and lower seeds of an invasive plant Xanthium italicum growing in Xinjiang, China, was investigated. All isolates from the seed capsules, the upper seeds, and the lower seeds were identified by 16S rRNA gene sequencing, and sequences were compared to bacterial databases to define operational taxonomic units (OTUs). Finally, we obtained 316 endophytic isolates corresponding to 58 OTUs based on 16S rRNA gene sequences. The most common OTU corresponded most closely to Bacillus zhangzhouensis and comprised 9.49% of all bacterial isolates. The richness and diversity of endophytes in lower seeds were higher than that of the upper seeds; moreover, the Chao estimator and Shannon index of endophytes in the lower seeds were approximate to that in the seed capsules. Bacillus and Staphylococcus were found as the common taxa in three different tissues that were investigated (OTUs belong to these genera constituted > 70% of the total community). The bacterial endophytic communities differed significantly among these three fruit tissues, especially Bacillus strains, which have been reported to contribute to plant growth promotion and stress resilience to their hosts in harsh environment; abundance of Bacillus species was in the following order: capsules (78 OTUs) > lower seeds (55 OTUs) > upper seeds (40 OTUs). The lower seeds harboring more Bacillus species might be responsible for their earlier seed germination compared with the upper seeds.