Screening of free-living rhizospheric bacteria for their multiple plant growth promoting activities

This study was conducted to identify and evaluate the antimicrobial activity of some Lactobacillus isolates of chicken origin. Among 90 isolates 14 Lactobacillus species were distinguished using MALDI-TOF mass spectrometry and 16S-ARDRA. The dominant species was L. salivarius (34.4%), followed by L. johnsonii (23.3%), L. crispatus (13.3%) and L. reuteri (11.1%). All lactobacilli were screened for antimicrobial activity against wild-type strains of Salmonella enterica, Escherichia coli, and Clostridium perfringens. Results from the agar slab method showed that all Lactobacillus isolates were able to produce active compounds on solid media with antagonistic properties against these pathogens. The highest sensitivity to lactobacilli was observed in C. perfringens strains, and the lowest in E. coli. Lactobacillus salivarius exhibited particularly strong antagonism towards all of the indicator bacteria. Strains of L. ingluviei and L. johnsonii and one strain of L. salivarius (10d) selectively inhibited the growth of C. perfringens. No antimicrobial activity of many Lactobacillus isolates was observed when cell-free culture supernatant was used in a well diffusion assay. All Lactobacillus isolates exhibited the ability to produce H2O2 and proved to be hydrophobic (excluding one of L. salivarius). [Int Microbiol 19(1):57-67 (2016)]Keywords: Lactobacillus spp. · avian lactobacilli · antimicrobial activity · gut health · poultry pathogens

Antimicrobial activity of

Background
Traditional agro-systems in arid areas are a bulwark for preserving soil stability and fertility, in the sight of “reverse desertification”. Nevertheless, the impact of desert farming practices on the diversity and abundance of the plant associated microbiome is poorly characterized, including its functional role in supporting plant development under drought stress.

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A drought resistance-promoting microbiome is selected by root system under desert farming.

Elephant grass (Pennisetum purpureum Schumach) and Hybrid Pennisetum (Pennisetum americanum × P. purpureum Schumach) are tall, fast-growing perennial C4 bunchgrasses that have been in recent developed as the most appropriate biomass feedstock in many countries for exploring various biofuel products. However, the challenges of increasing plant biomass yield and enhancing their stress tolerance, especially on marginal lands, have been existed for a long while. In the past several years, bacterial endophytes used as bio-fertilizers for improving crop production have offered an opportunity to facilitate high biomass yield of energy crops in a more sustainable manner. A total of 16 endophytic bacteria strains were isolated and purified from the roots of elephant grass, which were classified into four bacterial genera: Sphingomonas, Pantoea, Bacillus, and Enterobacter. Four strains, pp01, pp02, pp04, and pp06, represented four different genera, were then selected and tested in vitro for their plant growth promoting properties, effects on plant growth and salt stress tolerance of Hybrid Pennisetum. The inoculation with these four bacterial mixture demonstrated a significant plant growth promotion for Hybrid Pennisetum from the normal to salt stress conditions at 0, 50, 100, and 200 mM NaCl, respectively. The highest promotion rate for biomass yield was 116.01 and 81.72 % for shoot fresh weight and dry weight, respectively. The bacterial strains tested were shown to solubilize insoluble phosphate, fix nitrogen, produce indole acetic acid and ammonia, but only strains from Sphingomonas, Bacillus, and Enterobacter can produce siderophore. In addition, the endophyte strains tested were all able to successfully colonize the roots of Hybrid Pennisetum, reaching upto 12.12 ± 0.98 CFU/g fresh roots at the 3rd day of inoculation. The four endophytic bacteria from elephant grass significantly promoted plant growth and biomass yield, alleviated the harmful effects of salt stress on Hybrid Pennisetum. These bacteria have indicated some unique properties that are very valuable for exploiting bio-inoculants aiding in the efforts to establish a sustainable and large-scale feedstock production system for Hybrid Pennisetum, particularly, on the saline marginal lands.

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The endophytic bacteria isolated from elephant grass (Pennisetum purpureum Schumach) promote plant growth and enhance salt tolerance of Hybrid Pennisetum.

A total of 21 bacterial isolates (Azotobacter sp., 10 and fluorescent Pseudomonas sp., 11) were isolated from different rhizospheric soils in the vicinity of Aligarh city and characterized as per standard methods. These isolates were further tested for the production of indole acetic acid (IAA) in a medium with 0, 1, 2 and 5 mg/ml of tryptophan. A low amount (2.68-10.80 mg/ml) of IAA production was recorded by Azotobacter strains without tryptophan addition. Seven Azotobacter isolates showed high level (7.3 to 32.8 mg/ml) production of IAA at 5 mg/ml of tryptophan while at 1 and 2 mg/ml the production was in the range of 1.47 to 11.88 and 5.99 to 24.8 mg/ml, respectively. Production of IAA in fluorescent Pseudomonas isolates increased with an increase in tryptophan concentration from 1 to 5 mg/ml in the majority of isolates. In the presence of 5mg/ ml of tryptophan, 5 isolates of Pseudomonas produced high levels (41.0 to 53.2 mg/ml) of IAA while 6 other isolates produced IAA in the range of 23.4 to 36.2 mg/ml. Production of IAA was further confirmed by extraction of crude IAA from 3 isolates of Azotobacter (Azs1, Azs6 and Azs9 ) and three isolates of Pseudomonas (Ps1, Ps4 and Ps7) and subsequent TLC analysis. A specific spot from the extracted IAA preparation was found corresponding with the standard spot of IAA with same Rf value. Pseudomonas isolates (Ps1, Ps4 and Ps7) showed inhibitory effects on the growth of root elongation of Sesbania aculeata and Vigna radiata at all concentrations of tryptophan compared to the control. However, the isolates of Azotobacter (Azs1, Azs6 and Azs9) demonstrated stimulatory effects on both plants. Increasing the concentration of tryptophan from 1 mg/ml to 5 mg/ml resulted in decreased growth in both S. aculeata and V. radiata. On a comparative basis isolate Azs9 was most promising in promoting plant growth. On the other hand, high concentration of exogenous tryptophan could exhibit toxic effects on plant growth.

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Indole Acetic Acid Production by the Indigenous Isolates of Azotobacter and Fluorescent Pseudomonas in the Presence and Absence of Tryptophan

I: Basic Laboratory Techniques for Isolation, Cultivation, and Cultural Characterization of Microorganisms. II: Microscopy. III: Bacterial Staining. IV: Cultivation of Microorganisms: Nutritional and Physical Requirements, and Enumeration of Microbial Populations. V: Biochemical Activities of Microorganisms. VI: The Protozoa. VII: The Fungi. VIII: The Viruses. IX: Physical and Chemical Agents for the Control of Microbial Growth. X: Microbiology of Food. XI: Microbiology of Water. XII: Microbiology of Soil. XIII: Bacterial Genetics. XIV: Medical Microbiology. XV: Immunology. Appendices.

Microbiology : A Laboratory Manual

carefully written exercises, and a reasonable price combine to make Microbiology: Laboratory Theory & Application the best-selling microbiology lab manual. As a result, this laboratory manual was designed and written to be used in conjunction with the textbook Microbiology, fifth edition, by Lansing M. Prescott, John. Sample Laboratory Biosafety Manual for Microbiological Activities. According to the CDC Biosafety in Microbiological and Biomedical Laboratories (BMBL) 5th.

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