Use the acetylene reduction can be used for this purpose.

Dear Md.Tofazzai

Production of Indole-3-Acetic Acid by Endophytic Bacteria

It has been reported that endophytic bacteria may promote plant growth and suppress plant diseases, most likely by means similar to growth-promoting rhizobacteria. Furthermore, plant growth promotion is often greater when it is induced by endophytes rather than by bacteria restricted to the rhizosphere and the root surface . In this context, like rhizospheric bacteria, endophytic bacteria have been shown to have growth-promoting activity due to the production of phytohormones or enzymes involved in growth regulator metabolism, such as indole-3-acetic acid (IAA). The ability to synthesize phytohormones is widely distributed among plant-associated bacteria, and 80 % of the bacteria associated with plants are able to produce IAA

Improving Phytoremediation through Endophytic Bacteria

Metal-resistant endophytes are reported to be present in various hyperaccumulator plants growing in soils contaminated with heavy metals, and they play an important role in the survival and growth of such plants. Metal-resistant endophytes promote plant growth by various mechanisms, such as nitrogen fixation, solubilization of minerals, and production of phytohormones and siderophores .The study of endophytic bacteria is important not only for understanding their ecological role in interaction with plants but also for their possible biotechnological applications, such as bioremediation and phytoremediation. The genetic engineering of endophytic bacteria is easier than the genetic engineering of plants, plus gene expression within endophytes might be useful as a site-monitoring tool.

 In the past two decades, a lot of information on the role of endophytic microorganisms in nature has been collected. The ability to colonize internal host tissues has made endophytes valuable as a tool to improve crop performance. In this review, we address the major topics concerning the biotechnological potential of endophytic bacteria in agrobiology systems.

 Reported endophytes include both Gram-positive and Gram-negative bacteria and the classes Alpha-, Beta-, and Gammaproteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes . Approximately 300,000 plant species growing in unexplored areas of the earth are host to one or more endophytes and the presence of biodiverse endophytes in huge numbers plays an important role in the ecosystems with the greatest biodiversity, such as tropical and temperate rainforests , which are found extensively in Brazil and possess almost 20 % of its biotechnological source materials

The genus Burkholderia has been consistently described as culturable and endophytic, and the bacteria can colonize sugarcane. Burkholderia species are usually N2-fixing endophytes when associated with sugarcane. Additionally, other studies have described the importance of genus Burkholderia in the cultivation of sugarcane . Diazotrophic endophytic strains of Burkholderia have been found in banana, pineapple, and maize.

new approach to study the functional characteristics of endophytic bacteria. The authors presented the first metagenomic approach to analyze an endophytic bacterial community inside roots of rice.

Endophytic bacteria appear to originate from seeds , vegetative planting material  rhizosphere soil and the phylloplane. With the exception of seed-transmitted bacteria, which are already present in the plant, potential endophytes must first colonize the root surface prior to entering the plant. The initial processes of colonization of plant tissue by endophytic bacteria can be via stoma, lenticels, areas of emergence of lateral roots, and germinating radicles. Several authors have reported colonization of the secondary root emergence zone by bacterial endophytes

 Biotic interactions can improve agricultural productivity without costly and environmentally challenging inputs. Micromonospora strains have recently been reported as natural endophytes of legume nodules but their significance for plant development and productivity has not yet been established. The aim of this study was to determine the diversity and function of Micromonospora isolated from Medicago sativa root nodules.Micromonospora-like strains from field alfalfa nodules were characterized by BOX-PCR fingerprinting and 16S rRNA gene sequencing. The ecological role of the interaction of the 15 selected representativeMicromonospora strains was tested in M. sativa. Nodulation, plant growth and nutrition parameters were analyzed. Alfalfa nodules naturally contain abundant and highly diverse populations of Micromonospora, both at the intra- and at interspecific level. Selected Micromonospora isolates significantly increase the nodulation of alfalfa by Ensifer meliloti 1021 and also the efficiency of the plant for nitrogen nutrition. Moreover, they promote aerial growth, the shoot-to-root ratio, and raise the level of essential nutrients. Our results indicate that Micromonospora acts as a Rhizobia Helper Bacteria (RHB) agent and has probiotic effects, promoting plant growth and increasing nutrition efficiency. Its ecological role, biotechnological potential and advantages as a plant probiotic bacterium (PPB)

Nodules are new organs generated mainly in roots of leguminous plants, in cooperation with alpha and beta proteobacteria developed for biological nitrogen fixation. It was initially thought that only symbiotic nitrogen-fixing bacteria could exist inside healthy N2 fixing nodules. Recent studies have shown that they are frequently populated by a

 broad and heterogeneous range of both gram-positive and gram-negative bacteria Recently, the first intranodular actinobacteria have been described but from the first description in this environment, the number of actinomycetes found has increased and in fact even new species have been described.

Arbuscular Mycorrhizal Fungi (AMF) live in symbiosis with most crop plants and represent essential elements of soil fertility and plant nutrition and productivity, facilitating soil mineral nutrient uptake and protecting plants from biotic and abiotic stresses. These beneficial services may be mediated by the dense and active spore-associated bacterial communities, which sustain diverse functions, such as the promotion of mycorrhizal activity, biological control of soilborne diseases, nitrogen fixation, and the supply of nutrients and growth factors. In this work, we utilised culture-dependent methods to isolate and functionally characterize the microbiota strictly associated to Rhizophagus intraradices spores, and molecularly identified the strains with best potential plant growth promoting (PGP) activities by 16S rDNA sequence analysis. We isolated in pure culture 374 bacterial strains belonging to different functional groups—actinobacteria, spore-forming, chitinolytic and N2-fixing bacteria—and screened 122 strains for their potential PGP activities. The most common PGP trait was represented by P solubilization from phytate (69.7%), followed by siderophore production (65.6%), mineral P solubilization (49.2%) and IAA production (42.6%). About 76% of actinobacteria and 65% of chitinolytic bacteria displayed multiple PGP activities. Nineteen strains with best potential PGP activities, assigned to Sinorhizobium meliloti, Streptomyces spp., Arthrobacter phenanthrenivorans, Nocardiodes albus, Bacillus sp. pumilus group, Fictibacillus barbaricus and Lysinibacillus fusiformis, showed the ability to produce IAA and siderophores and to solubilize P from mineral phosphate and phytate, representing suitable candidates as biocontrol agents, biofertilisers and bioenhancers, in the perspective of targeted management of beneficial symbionts and their associated bacteria in sustainable food production systems.

Endophytic bacteria are believed to elicit plant growth in many ways, including the following: helping plants acquire nutrients, e.g., via nitrogen fixation, phosphate solubilization, or iron chelation; preventing infections via antifungal or antibacterial agents; out-competing pathogens for nutrients by producing siderophores; or establishing the plant’s systemic resistance and producing phytohormones. However, the effects and functions of endophytes in plants have not been comprehensively defined. The challenge and goal is to be able to manage microbial communities to favor plant colonization by beneficial bacteria. This will be possible when a better knowledge of endophyte ecology and molecular interactions is attained.

Regards,

Prem Baboo

15N Foliar dilution method can be used to confirm N-fixation.

HELLO,

Grow the plants using Isotopes of nitrogen and assay for acetylene reduction, it would give the exact measure of nitrogen fixation. 

I usually use NFB meduium to check N2 fixation activity

Thanks to all scholars for sharing your experiences. Would you please share a reference or detailed protocol?