Antimicrobial properties of endophytic actinomycetes isolated from <Emphasis Type="Italic">Combretum latifolium</Emphasis> Blume,a medicinal shrub from Western Ghats of India

Endophytic actinomycetes were isolated from Combretum latifolium Blume (Combretaceae),Western Ghats of Southern India and identified by its characteristic culture morphology and molecular analysis of 16S rRNA gene sequences. In this survey of endophytic actinomycetes, a total of 117 isolates representing 9 different genera of endophytic actinomycetes were obtained using four different isolation media and several of them seemed to be novel taxa. Streptomyces genera (35%) was the most frequently isolated strains, followed by Nocordiopsis (17%) and Micromonospora (13%). ISP-4 medium recovered more isolates (47%) when compared to rest of the media used. Preliminary antibacterial activity of the isolates was carried out by confrontation test. Ethyl acetate fraction of selected isolates in disc diffusion assay exhibited broad spectrum antimicrobial activity against test human pathogens. All Streptomyces spp. strains displayed significant antimicrobial activity against test pathogens. Strain CLA-66 and CLA-68 which are Nocordipsis spp. inhibited both bacterial and fungal pathogens where as other isolates inhibited atleast three test human pathogens in disc diffusion assay. Antimicrobial screening of endophytic actinomycetes from this host may represent a unique potential niche for antimicrobial compounds of industrial and pharmaceutical applications. This work is the first comprehensive report on incidence of potential endophytic actinomycetes inhabiting C. latifolium Blume.     

Diversity of endophytic fungal and bacterial communities in <Emphasis Type="Italic">Ilex paraguariensis</Emphasis> grown under field conditions

The composition and diversity of the endophytic community associated with yerba mate (Ilex paraguariensis) was investigated using culture-depending methods. Fungi were identified based on their micromorphological characteristics and internal transcribed spacer rDNA sequence analysis; for bacteria 16S rDNA sequence analysis was used. Fungal and bacterial diversity did not show significant differences between organ age. The highest fungal diversity was registered during fall season and the lowest in winter. Bacterial diversity was higher in stems and increased from summer to winter, in contrast with leaves, which decreased. The most frequently isolated fungus was Fusarium, followed by Colletotrichum; they were both present in all the sampling seasons and organ types assayed. Actinobacteria represented 57.5 % of all bacterial isolates. The most dominant bacterial taxa were Curtobacterium and Microbacterium. Other bacteria frequently found were Methylobacterium, Sphingomonas, Herbiconiux and Bacillus. Nitrogen fixation and phosphate solubilization activity, ACC deaminase production and antagonism against plant fungal pathogens were assayed in endophytic bacterial strains. In the case of fungi, strains of Trichoderma, Penicillium and Aspergillus were assayed for antagonism against pathogenic Fusarium sp. All microbial isolates assayed showed at least one growth promoting activity. Strains of Bacillus, Pantoea, Curtobacterium, Methylobacterium, Brevundimonas and Paenibacillus had at least two growth-promoting activities, and Bacillus, Paenibacillus and the three endophytic fungi showed high antagonistic activity against Fusarium sp. In this work we have made a wide study of the culturable endophytic community within yerba mate plants and found that several microbial isolates could be considered as potential inoculants useful for improving yerba mate production.     

Antimicrobial endophytic fungal assemblages inhabiting bark of <Emphasis Type="Italic">Taxus baccata</Emphasis> L. of Indo-Burma mega biodiversity hotspot

Fungal endophytes were isolated from inner bark of Taxus baccata L., an important source of potent anticancer drug taxol. Bark samples were collected from two locations of Arunachal Pradesh, India, part of the Indo-Burma mega biodiversity hotspot, during two seasons i.e. monsoon and winter. Altogether 77 fungal strains representing 18 genera were isolated from T. baccata bark during the present investigation. The colonizing frequency was recorded as 38.5% and the fungal community comprised of 78% of Hyphomycetes, 5.2% of Coelomycetes, 2.6% of Zygomycetes and Ascomycetes and 9.1% of sterile mycelia. Most common and frequently isolated genera were Fusarium, Penicillium and Aspergillus. Simpson and Shannon diversity indices indicated higher species diversity during monsoon than during winter seasons irrespective of the locations. The two locations harbored 5 to 37 endophyte species and the similarity index was low during winter and high during monsoon. Ethyl acetate extract of fermentation cultures of these fungi were tested for their antimicrobial activity against a panel of human pathogenic Gram-positive and Gram-negative bacteria and fungi. Fifteen fungal isolates out of the isolated strains displayed antimicrobial activity. An endophytic fungus, identified as Fusarium sp. displayed significant antimicrobial activity against all the test pathogens.     

Endophytic <Emphasis Type="Italic">Alcaligenes</Emphasis> Isolated from Horticultural and Medicinal Crops Promotes Growth in Okra (<Emphasis Type="Italic">Abelmoschus</Emphasis><Emphasis Type="Italic">esculentus</Emphasis>)

The potential of endophytic bacteria to act as biofertilizers and bioprotectants has been demonstrated, and considerable progress has been made in explaining their role in plant protection. In the present study, three endophytic bacterial strains (BHU 12, BHU 16 isolated from the leaves of Abelmoschus esculentus, and BHU M7 isolated from the leaves of Andrographis paniculata) were used which displayed high sequence similarity to Alcaligenes faecalis. The biofilm formation ability of these endophytic strains in the presence of okra root exudates confirms their chemotactic ability, an initial step for successful endophytic colonization. Further, reinoculation of spontaneous rifampicin-tagged mutants into okra seedlings revealed a CFU count above 10⁵ cells g^?1 of all three endophytic strains in root samples during the first 15 days of plant growth. The CFU count increased up to 10¹³ by 30 days of plant growth, followed by a gradual decline to approximately 10¹⁰ cells g^?1 at 45 days of plant growth. Systemic endophytic colonization was further supported by 2, 3, 5-triphenyl tetrazolium chloride staining and fluorescence imaging of ds-RED expressing conjugants of the endophytic strains. The strains were further assessed for their plausible in vivo and in vitro plant growth-promoting and antagonistic abilities. Our results demonstrated that the endophytic strains BHU 12, BHU 16, and BHU M7 augmented plant biomass by greater than 40 %. Root and shoot lengths of okra plants when primed by BHU 12, BHU 16, and BHU M7 increased up to 34 and 14.5 %, respectively. The endophytic isolates also exhibited significant in vitro antagonistic potential against the collar rot pathogen Sclerotium rolfsii. In summary, our results demonstrate excellent potential of the three endophytic bacterial strains as biofertilizers and biocontrol agents, indicating the possibility for use in sustainable agriculture.     

Genome analysis reveals insights of the endophytic <Emphasis Type="Italic">Bacillus toyonensis</Emphasis> BAC3151 as a potentially novel agent for biocontrol of plant pathogens

Diseases caused by phytopathogenic microorganisms account for enormous losses for agribusiness. Although Bacillus species are recognized as being antimicrobial producers and some may provide benefits to plants, the association between Bacillus toyonensis and plants has not been studied. In this study, the whole-genome sequenced endophytic B. toyonensis BAC3151, which has demonstrated antimicrobial activity and quorum sensing inhibition of phytopathogenic bacteria, was investigated for its potential for the production of compounds for biocontrol of plant pathogens. Four whole-genome sequenced B. toyonensis strains shared 3811 protein-coding DNA sequences (CDSs), while strain-specific CDSs, such as biosynthetic gene clusters of antimicrobials, were associated with specific chromosomal regions and mobile genetic elements of the strains. B. toyonensis strains had a higher frequency of putative bacteriocins gene clusters than that of Bacillus species traditionally used for the production of antimicrobials. In addition, gene clusters potentially involved in the production of novel bacteriocins were found in BAC3151, as well as biosynthetic genes of several other compounds, including non-ribosomal peptides, N-acyl homoserine lactonase and chitinases, revealing a genetic repertoire for antimicrobial synthesis greater than that of other Bacillus strains that have demonstrated effective activity against phytopathogens. This study showed for the first time that B. toyonensis has potential to produce various antimicrobials, and the analyses performed indicated that the endophytic strain BAC3151 can be useful for the development of new strategies to control microbial diseases in plants that are responsible for large damages in agricultural crops.     

Plant growth-promoting potential of endophytic bacteria isolated from roots of wild <Emphasis Type="Italic">Dodonaea viscosa</Emphasis> L.

Dodonaea viscosa, a wild and perennial shrub that can tolerate harsh environmental conditions, was used for the isolation of its endophytic bacteria and their potential was explored for the promotion of Canola growth. The bacteria identified through 16S rRNA gene sequencing, belonged to ten different genera namely Inquilinus, Xanthomonas, Pseudomonas, Rhizobium, Brevundimonas, Microbacterium, Bacillus, Streptomyces, Agrococcus and Stenotrophomonas. All the strains produced small amount of IAA (indole acetic acid) in the absence of tryptophan and comparatively more in the presence of tryptophan. All the bacterial strains were positive for ammonia production, cellulase and pectinase activity, but few of them showed phosphate solubilization, siderophore and hydrogen cyanide production. Only three strains showed ACC (1-aminocyclopropane-1-carboxylate) deaminase activity when tested using in-vitro enzyme assay. Members of genera Bacillus, Pseudomonas and Streptomyces showed positive chitinase, protease and antifungal activity against two phytopathogenic fungi Aspergillus niger and Fusarium oxysoprum, while members of Xanthomonas, Pseudomonas and Bacillus showed significant root elongation of Canola which could be related with their positive plant-growth-promoting (PGP) traits. Among the three plant growth promoting Bacillus strains, B. idriensis is never reported before for its PGP activities. These results showed the potential of Dodonaea viscosa endophytic bacteria as PGPBs, which in future can be further explored for their host range/molecular mechanisms.     

Bioactive sesquiterpene,plasticizer, and phenols from the fungal endophytes of <Emphasis Type="Italic">Polygonum chinense</Emphasis> L.

There is a constant need for novel antibiotic and antioxidant sources due to the ever-increasing resilience of pathogens and the occurrence of chronic diseases. The natural sources of these agents have advantages due to lower production cost, structural variation, and uses of active compounds for pharmaceutical uses. The microbes living in planta termed “endophytes” are alternative sources of host bioactive compounds. In this study, ten endophytic fungi were isolated from Polygonum chinense L. and identified by sequencing of the internal transcribed spacer regions. The fungal strains were fermented and the ethyl acetate extracts were evaluated for antimicrobial and antioxidant capacities. Almost 80% of the endophytes showed antibacterial potency against one or more pathogenic bacteria. Among all strains, Penicillium canescens showed broad-spectrum antimicrobial activity against gram-positive and gram-negative pathogens as well as significant antioxidative and DNA protective capacities. The strain Fusarium chlamydosporum displayed significant anti-radical (126.8?±?6.7 μg/ml) and ferric reducing (84.7?±?2.1 mg AA/g dry extract) capacities. The bio-autography, chromatography, and mass spectroscopy analyses of P. canescens extract revealed the presence of sesquiterpene (germacrene), plasticizer (phthalic acid ester) along with phenolic acids, flavonoid (quercetin), and short chain hydrocarbons. The secondary metabolites of F. chlamydosporum were identified with phenolic acids as bioactive compounds by chromatography and mass spectroscopy. This study indicates P. chinense endophytes as potential sources of antimicrobial and antioxidant compounds for novel drug discovery.     

Efficacy of bacterial seed treatments for the control of <Emphasis Type="Italic">Fusarium verticillioides</Emphasis> in maize

Maize colonization by the phytopathogenic fungi Fusarium verticillioides leads to economical and food quality losses and also implicates potential health risks. In order to control this fungal species different strategies are being considered. In the present work we investigated the in situ effects of the use of two in vitro proven bacterial biological control agents against Fusarium verticillioides, using maize seedlings grown in greenhouse conditions. The treatment of maize seeds with Fusarium verticillioides 10⁷ spores ml^?1 negatively affected the length of the stem and the weight of the root systems of resultant seedlings, and also reduced the numbers of non-rhizospheric organisms with ammonification and nitrification activities. The addition of Bacillus amyloliquefaciens or Microbacterium oleovorans, at a concentration of 10⁹ colony forming units ml^?1, to the seeds significantly reduced Fusarium verticillioides count at the root inner tissues of resultant seedlings. When testing the impact of bacterial treatments on soil populations, no alterations with respect to control numbers of organisms with nitrification, ammonification or cellulolytic potentials were observed. Culturable bacterial richness and diversity calculated at the rhizoplane and root inner tissues of maize seedlings neither changed in bacterized treatments when compared to control treatment. Our study showed that the Fusarium verticillioides in vitro proven antagonists, Bacillus amyloliquefaciens and Microbacterium oleovorans (at 10⁹ colony forming units ml^?1), were also effective at greenhouse conditions without causing major changes in culturable rhizospheric and endophytic microbial richness and diversity.     

Endophytism and bioactivity of endophytic fungi isolated from <Emphasis Type="Italic">Combretum lanceolatum</Emphasis> Pohl ex Eichler

We report the isolation and identification of endophytic fungi from Combretum lanceolatum Pohl ex Eichler. Further, we evaluated the relationships of fungi with the host plant and tested bioactivities of isolates. The fungi were isolated from disinfected root fragments and plated onto potato dextrose agar. Root pieces were also used to quantify fungal structures associated with the roots. Identification of fungi was carried out by characterization of morphological features and sequencing of the ITS region. Endophytism was confirmed by inoculation of endophyte-free seedlings followed by microscopic examination. The extract was obtained by maceration of the mycelium in ethyl acetate for antioxidant and antimicrobial evaluations. A total of 112 strains belonging to nine different species were isolated, the major classes were Dothideomycetes and Sordariomycetes. C. lanceolatum is colonized by dark septate endophytes (DSE), evidenced by the presence of microsclerotia and melanized hyphae. There is also co-colonization with mycorrhizal fungi in the same root fragments. Seedling inoculation experiments revealed that C. perangustum-95C and M. phaseolina-46C showed association with the seedlings of C. lanceolatum and differentiated microsclerotia and dark septate hyphae, indicating that these species are DSE. In the antimicrobial test, the D. phaseolorum-92C extract had the highest zones of inhibition against S. aureus and E. coli, respectively. The results showed that 100 % of the extracts have antioxidant activity ranging from low to moderate. All endophyte species had antioxidant and antimicrobial activities that were directly proportional to the dose-responses. Future research will involve chemical characterization and structural elucidation of bioactive compounds.     

Canopy tree species and openness affect foliar endophytic fungal communities of understory seedlings

There is growing evidence demonstrating the diversity of foliar endophytic fungi and their ecological roles in the survival of tree seedlings. However, the factors that shape fungal communities in tree seedlings within natural forest ecosystems remain poorly understood. Here, we evaluated the composition of foliar endophytic fungi growing in current-year seedlings of Cornus controversa and Prunus grayana in a cool temperate deciduous forest through a seed-sowing experiment and fungal isolation. The composition of endophytic fungi was affected by canopy tree species, canopy openness, and time after germination. In total, 27 and 22 fungal taxa were isolated from C. controversa and P. grayana seedlings, respectively. The dominant fungal taxa in both seedling species were Colletotorichum spp., and their isolation frequencies were higher under C. controversa canopies than under P. grayana canopies; the frequencies also increased with time after germination. These results suggest that overstory tree species strongly influences the endophytic fungal communities of understory seedlings.     

Characterization of a Gloverin-Like Antimicrobial Peptide Isolated from Muga Silkworm, <Emphasis Type="Italic">Antheraea assamensis</Emphasis>

Antimicrobial peptides (AMPs) are produced in all living organisms including insects in a non-specific manner, and act as innate immune defense arsenal against the invading pathogens. Muga silkworm (Antheraea assamensis) larvae were injected with Candida albicans and AMPs were isolated from the hemolymph after extracting with methanol, acetic acid and water mixture (90:1:9) and evaluated for antimicrobial activity against fungal and bacterial pathogens. Further purification was done through successive semipreparative and analytical reversed phase HPLC using C-18 column. The obtained fractions were collected, lyophilized and tested for antimicrobial activity. Among the HPLC fractions, one showed highest activity with MIC value of 64 µg/ml against Gram-negative bacteria, Escherichia coli and Enterobacter cloacae. Purity of this isolated peptide was confirmed by SDS-PAGE and TLC, and its molecular mass was determined as 9.052 kDa by MALDI-TOF mass spectrometry. From the mass fingerprinting analysis of this peptide after trypsin digestion a peptide fragment with molecular mass of 2622.7 Da was obtained. De novo sequencing of this peptide fragment following MS/MS analysis identified few amino acid residues as “KSGGGGWGS” with a total score of 46.9 with gloverin peptide of A. mylitta. The peptide inhibited biofilm formation of the Gram-negative bacterial pathogens. SEM study revealed that peptide disrupted bacterial cell wall to leach out intracellular materials and may be the major target for its antimicrobial activity.     

Plant growth promoting potential of bacterial endophytes in novel association with <Emphasis Type="Italic">Olea ferruginea</Emphasis> and <Emphasis Type="Italic">Withania coagulans</Emphasis>

Microbially unexplored medicinal plants can have a genetically diverse microbial population with multi-functional plant growth promoting traits. In this aspect, 75 endophytic bacterial isolates with plant growth promoting traits were isolated from Withania coagulans Dunal and Olea ferruginea Royal. Many of these bacteria were able to solubilize phosphate, produce indole-3-acetic acid, ammonia as well as hydrogen cyanide, synthesize extracellular enzymes and show antagonistic activities against plant pathogenic fungi under in vitro conditions. These isolates were also characterized by morphological and biochemical analysis. Furthermore, four representative isolates with pronounced plant growth promoting activities were identified as Enterobacter cloacae, Enterobacter dissolvens, Enterobacter hormaechei and Cronobacter sakazakii by 16S rDNA sequencing analysis. This work for the first time, reported the isolation of endophytic bacteria, the novel association form selected plants, Withania coagulans and Olea ferruginea. The explored endophytes might have great potential in the field of biocontrol and plant growth promoting for sustainable agricultural practices.     

Defense Responses and Changes in Symbiotic Gut Microflora in the Colorado Potato Beetle <Emphasis Type="Italic">Leptinotarsa decemlineata</Emphasis> under the Effect of Endophytic Bacteria from the Genus Bacillus

Phytophagous insects and host plants have a complex of microsymbionts and make up a united co-evolving system with them. Microsymbiotic complexes are actively involved in stress responses of macrosymbionts. We established that a treatment of potato plants with endophytic bacterial strains Bacillus thuringiensis var. thuringiensis-5689, B. th. var. kurstaki-5351, and Bacillus subtilis 26D decreased the survival rate of the plant feeder, Colorado potato beetle Leptinotarsa decemlineata Say. The B. th. strains suppressed phenoloxidase and acetylcholinesterase activities in the beetle hemolymph. An antagonistic relationship was found between endophytic bacteria B. subtilis 26D and beetle symbiotic bacteria from the genera Acinetobacter and Enterobacter, with the former being able to suppress the growth of endophytic colonies. The recombinant B. subtilis strain 26D Cry, containing the B. th. var. kurstaki δ-endotoxin cry1Ia gene, combined the ability of the original B. subtilis 26D strain to suppress the development of beetle symbionts and immune responses with a production of the Cry toxin, thus leading to a high mortality of the phytophage.     

Effect of the biocontrol bacterium <Emphasis Type="Italic">Bacillus amyloliquefaciens</Emphasis> on the rhizosphere in ginseng plantings

Panax ginseng is an important medicinal herb due to its ability to strengthen the human immune system. However, due to the increasing needs of ginseng in medicine, the continuous cropping of ginseng has become more common and has resulted in increased problems with fungal decay. Thus, chemical fungicides are commonly used in ginseng plantings, which have caused fungicide residue problems. As an alternative control measure, biocontrol bacteria can be used to manage fungal pathogens. Additionally, these bacteria are environmentally friendly and can also improve stress tolerance in plants. In this study, an antifungal bacterial strain, TB6, that possesses ACC deaminase activity was isolated from the rhizosphere of ginseng plants. This strain was identified as Bacillus amyloliquefaciens. TB6 was applied to 2-year-old ginseng seedlings for a 2-year period, and its impact on the soil rhizosphere was evaluated. The results revealed that strain TB6 decreased fungal abundance and diversity; improved urease, catalase, and phosphatase activities; and decreased the cellulase activity of the rhizosphere soil. In addition, strain TB6 also promoted root growth and increased the fresh weight of ginseng roots, in addition to increasing polyphenol oxidase and catalase activities. These results may have practical implications for the use of biocontrol bacteria in ginseng plantings.     

Isolation of <Emphasis Type="Italic">Lactobacillus</Emphasis> strains from shellfish for their potential use as probiotics

Microorganisms intended for use as probiotics in aquaculture should exert antimicrobial activity and be regarded as safe not only for their aquatic hosts but also for their surrounding environments and humans. The objective of this work was to investigate antimicrobial activity against various pathogens, bile salt tolerance, and acid tolerance of 65 presumptive Lactobacillus spp. isolated from shellfish samples. Four strains (HL1, HL12, HL20, and JL28) were selected after qualitatively identifying high levels of antimicrobial activity against bacteria including Staphylococcus aureus, Salmonella typhimurium, Salmonella enteritidis, Escherichia coli O157:H7, Vibrio ichthyoenteri, Edwardsiella tarda, Streptococcus iniae, and V. parahaemolyticus. The sequence analysis of their 16S rRNA genes revealed that the four strains belong to the Lactobacillus plantarum species. In addition, their survivability was tested in bile salt and acidic conditions to show their potential use as probiotics in the gastrointestinal tract.     

Efficacy of botanical extracts from Brazilian savannah against <Emphasis Type="Italic">Diabrotica speciosa</Emphasis> and associated bacteria

Botanical extracts are a plentiful resource of molecules with different biological activities, such as insecticides and antimicrobial pesticides. In this context, the aim of this work was to evaluate the efficacy of botanical extracts from the Brazilian savannah against Diabrotica speciosa and bacterial strains isolated from the gut of this insect under aseptic conditions. The bacterial isolates were identified by genomic and proteomic approaches, and bioassayed against eighteen botanical extracts in vitro. The best results of bacterial inhibitions were obtained for the extracts of Casearia sylvestris and Psidium laruotteanum. Fractions of C. sylvestris and P. laruotteanum, quantitatively evaluated by chromatographic analyses, showed a relationship between the bactericidal activity and phytochemical profile. In vivo assays showed that P. laruotteanum was also effective for the control of D. speciosa. Those results show that selected natural products can have both antimicrobial and insecticidal activities.     

Antibiotic activity of bacterial endobionts of basidiomycete fruit bodies

Bacterial strains (93 isolates) capable of growth on full-strength nutrient media were isolated from 86 fungal fruit bodies collected in the Moscow region. Antimicrobial activity of the endobiont isolates against 12 bacterial and fungal test strains (including drug-resistant ones) was studied in submerged cultures. Most of the strains (84.9%) were found to produce antibiotic compounds with different antimicrobial properties, including antifungal activity in 18.3% of the strains. Morphological characteristics and analysis of the 16S rRNA gene sequences were used to determine the taxonomic position of 16 bacterial strains of the following 10 species: Bacillus subtilis, Ewingella americana, Pseudomonas sp., Stenotrophomonas maltophilia, as well as Achromobacter spanius, B. licheniformis, Hafnia paralvei, Micrococcus terreus, Nocardia coeliaca, and St. rhizophila, which have not been previously known to be endobionts of basidiomycete fruit bodies. Antimicrobial activity of A. spanius, E. americana, H. paralvei, M. terreus, N. coeliaca, and St. rhizophila has not been reported previously. Complex mechanisms of symbiotic relations between fungi and bacteria, including those associated with antibiotic formation, probably developed in the course of co-evolution.     

Isolation Purification and Characterization of Antimicrobial Peptides from <Emphasis Type="Italic">Cuminum cyminum</Emphasis> L. Seeds

In this work, antimicrobial peptides from Cuminum cyminum L. seeds were isolated and purified for the first time by 50% ethanol extraction, C18 reverse phase column chromatography and ion exchange chromatography for separation different peptides fraction. Then isolated fractions were characterized by Gel electrophoresis (SDS-PAGE), high-pressure liquid chromatography and the peptides components and molecular weights were determined by liquid chromatography and mass spectrometry. The extracts were tested against some strains of bacteria (E. coli and Staphylococcus aureus) and one strain of fungi (Candida albicans) using well diffusion and broth dilution assays. The extracts from C. cyminum L. seeds demonstrated a high degree of activity (some antibacterial effect) against the bacteria strains and аntifungal activity against the Candida albicans. However, the study indicates that the crude peptide extracts from C. cyminum L. seeds have promising antimicrobial and antioxidant activities that can be harnessed as leads for potential bioactive compounds.     

Identification of interior salt-tolerant bacteria from ice plant <Emphasis Type="Italic">Mesembryanthemum crystallinum</Emphasis> and evaluation of their promoting effects

Endophytic bacteria can stimulate host plant development. Insufficient information is available about NaCl-tolerant bacteria that colonize ice plants (Mesembryanthemum crystallinum) in their habitats. In this study, a culture-dependent method was used to isolate endophytic nitrogen-fixing bacteria from ice plants, and the resulting cultures were screened for salt-stress tolerance in vitro. A total of 17 salt-tolerant bacteria were obtained. The majority of the isolates grew well in 2.05 M NaCl with a maximum tolerance at 3.59 M. Most of the strains were Gram-positive bacteria with various plant growth-promoting traits. The 16S rRNA gene sequences revealed that the 17 isolates were distributed within three genera and corresponded to the bacterial species Halomonas sp., Bacillus sp., and Planococcus sp. Inoculation of cabbage (Brassica olereacea) seeds with selected strains showed that the strain MC1 promoted seed germination, and the same strain significantly increased root dry weight under saline stress by 24.5%. Our study suggests that ice plants naturally accommodate a variety of salt-tolerant endophytic bacteria and that these bacteria are able to relieve abiotic stress during plant growth.     

Probiotic potential of novel <Emphasis Type="Italic">Lactobacillus</Emphasis> strains isolated from salted-fermented shrimp as antagonists for <Emphasis Type="Italic">Vibrio parahaemolyticus</Emphasis>

Lactobacillus strains have been considered good candidates as biological control agents for prevention or treatment of plant and animal infections. One L. plantarum strain FB003 and three strains (FB011, FB081, and FB110) which closed to L. sakei were isolated from fermented and salted shrimp and their abilities in inhibiting growth of Vibrio parahaemolyticus were characterized. These strains were selected as potential probiotics based on their oro-gastro-intestinal resistance, gut colonization, adhesion to Caco-2 cells, antimicrobial activities, antibiotic resistance, and safety aspects. Results of this study revealed that these isolates possessed high aggregation activities against pathogens in host intestines. Strain FB011 strain showed higher coaggregation and immunomodulatory activity in the gastro-intestinal tract than L. plantarum. These difference effects of Lactobacillus strains provide valuable information about using them to prevent Vibrio infections in the aquaculture industry.