Endophytic Bacteria In Plants And Their Effect On Plant-Growth-Promoting Activity Term Paper Examples

There exists about 300,000 plant species on earth, and every individual plant hosts one or more endophytes. However, it is just a few of these plants that have been researched relative to their endophytic biology. Hence, the chance for isolation of new, as well as, interesting endophytic bacteria in plants are important. Endophytic bacteria can be referred to as bacteria that can be isolated from tissues of a surface-disinfected plant or bacteria extracted from inside of a plant, which cause no visible negative effects to the plant. Almost every plant is populated by varied bacteria referred to as endophytes. Majority of these bacteria attacks varied parts of the apoplast of the plant, which include the cell walls’ intercellular spaces, as well as xylem vessels. A number of these bacteria have the ability to colonize the plants’ reproductive organs, for instance, seeds, flowers, as well as fruits. Within the plant, the endophytic bacteria do not usually result in any significant changes, in morphology just as root-nodule symbionts do. They as well do not lead to any symptoms of a disease, contrary to phytopathogens.
The interactions between the endophytes and their hosts are complex and entail antagonism, as well as mutualism. Plants severely restrict the endophytes’ growth, while the endophytic bacteria employ a number of mechanisms to slowly conform to their living surroundings. In order that there can be maintenance of symbiosis that is stable, endophytes secret a number of compounds, which enhance plants’ growth and assist them in adapting better to the surrounding.
Recently, it has been exhibited that endophytic bacteria can as well have positive effects on the host plants. These may include effects like promotion of growth, as well as biological control of pathogens. A number of research studies have demonstrated that the endophytes potential of promoting growth is more than that exhibited by the rhizosphere microbes, even though the functions of endophytic bacteria in growth plant are yet to be fully apprehended. This paper is aimed at exploring the effects of endophytic bacteria on plant growth promoting activity.
There has been the discovery of different mechanisms, employed by the endophytic bacteria in regard to in the promotion of plant growth. These include an indirect mechanism where they help plants in acquiring nutrients, through fixation of nitrogen, solubilization of phosphate, via prevention of infections by pathogens, among others. This ability to help the plants is enhanced through via production of antibacterial or antifungal agents, where they outcompete pathogens for nutrients through production of siderophore.
Inoculation of plants with plant growth promoting bacteria has been demonstrated to have a great effect on growth of the plant. For instance, in a research study that was carried out in order to ascertain the effects of varied local strains of plant-growth-promoting rhizobacteria, as well as nitrogen fertilizer on yield and growth of sweet potato. Four strains of plant-growth-promoting rhizobacteria, which include Azospirillum brasilense SP7, Klebsiella sp. and Bacillus sphaericus UPMB 10 UPM SP9, Erwinia sp. UPM SP10, as well as a non-inoculated control together with three nitrogen fertilizer levels, were used. In this study, the plants that were inoculated with the plant growth promoting rhizobacteria together with a third of the normal rate produced the highest storage root dry weight in comparison to plants that were not inoculated. Inoculation with the plant growth promoting rhizobacteria also raised the concentrations of K, P and N in shoots as well as storage root.
Phytostimulation is among the indirect mechanisms employed by endophytic bacteria to enhance plant growth promoting activity. For better growth, plants need 16 essential elements such as C, O, P, N, and H, among others. These essential elements have to be availed to plants so that they can access their growth, as well as development in the form of chemical that they get from soil, atmosphere, organic matter and water. Endophytes, as well serve a crucial role in the intake of these nutrients. They evoke varied action modes in tall fescue P deficiency adaptation, and they stimulate raised intake of N. Bacterial endophytes secrete a broad range of phytohormones, for instance gibberellic acids cytokinins, as well as auxins. Burkholderia vietnamiensis, which is an endophytic bacterium that is diazotrophic isolated from Populus trichocarpa, wild cottonwood, secretes indole acetic acid that enhances the plant growth. This secretion of indole acetic acid has been affirmed in an experiment that compared controls that were not inoculated and B. vietnamiensis inoculated plants on nitrogen free media, where inoculated plants were observed to gain more dry weight and more content of nitrogen.
Plant growth promoting activity by endophytic bacteria has been demonstrated through their antimicrobial activity. Majority of the endophytes obtained from plants is recognized for their ability to exhibit antimicrobial activity. They aid in control of microbial pathogens in plants. For instance, in a study where endophytic bacteria isolated from medicinal plants were shown to exhibit a bioactivity for a wide spectrum of pathogenic microbe. Out of 37 endophytes that were isolated all at once from Tectona grandis L., as well as Samanea saman Merr. 18 demonstrated their ability to secrete inhibitory substances, which were effectual against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus while three isolates demonstrated their ability to inhibit Candida albicans growth in vitro. In another study that analyzed the endophytic microorganisms’ bioactivity obtained from the medicinal plant, Tylophora indica, against Fusarium oxysporum and Sclerotinia sclerotiorum demonstrated that the endophytic bacteria inhibited the growth of these microorganisms.
Endophytic bacteria are known to have the capability to synthesize bioactive compounds, which are utilized by plants to defend themselves against pathogens while a number of these compounds have demonstrated to be helpful in the novel drug discovery. It has been reported by recent studies that many natural products, which includes terpenoids, flavonoids, steroids, and alkaloids, from endophytes. Majority of the bioactive compounds obtained from endophytic bacteria is recognized to have roles of immunosuppressants, antibiotics, and biological control agents, among others.
The responses of microbial community in soils stipulated by Lolium multiflorum, plants of the annual grass, having contrastive infection levels with the endophyte Neotyphodium occultans were researched. Conditioning of soil by highly infected plants had effects on catabolic profiles of the soil and had a tendency to raise fungal activity in the soil. A bacterial community structures shift was observed as no alterations were observed for the fungal community. Soil reactions were shown to become apparent even with no alterations in the biomass of the plant acting as host or total nitrogen content or soil organic carbon, proposing that there was a modification of the rhizo depositions of the host by the endophyte in the course of the conditioning phase.
Endophytic bacteria are regarded as an effectual biological control agent alternative to control by use of chemicals. Endophytic bacteria have been depicted to serve a crucial role in control of insect herbivory in grasses, as well as, in conifers. For instance, Bacillus subtilis, endophytic bacteria, obtained from Speranskia tuberculata, Bge., Baill was discovered to show strong antagonistic effects against the pathogen B. Cinereain in vitro research studies.
Nutrient cycling, which is a very crucial procedure, which takes places incessantly in order to balance the nutrients in existence and avail it for each part of the ecosystem. Biological breakdown of the dead biomasses turns into a single major phase in order to take back the used nutrients to the ecosystem that in turn again is availed to the organisms. The availed nutrients then turn into a cyclic chain procedure. Even though several saprophytic organisms serve a key function in this process, a few research studies have demonstrated that endophytic bacteria have a crucial function in biological degradation of its host plants’ litter. In the course of biological degradation of the litter, the endophytic bacteria infect first within the plants, as well as enhance the saprophytic microorganisms to follow up on through antagonistic interaction, and hence raising the decomposition of the litter. In another research study, it was exhibited that every endophytic bacterium had the capability to breakdown organic components, which include cellulose, lignin, as well as hemicelluloses, nevertheless the predilections of a number of endophytic groups with respect to organic compounds showed significance difference.
There has been a great deal of interest in the recent years among investigators in the endophytic bacteria, which has been made enhanced by the easy isolation methods, identifications, as well as current molecular biology tools. A number of compounds that are bioactive that have beneficial effects on the environment, industries, as well as agriculture, are secreted by endophytic bacteria. Because of their great significance to plants, research scientists have already begun making use of them for more novel compounds, as well as their newer function to the environment. In this paper, the conclusion has been made that bacteria are largely involved in secretion of pharmaceutically significant compounds in the plants. Generally, endophytic bacterial community aids in enhancing growth of the plants through production of different hormones of growth. Use of different innovative tools of biotechnology will assist in fortifying the understanding of interactions of plants and endophyte, perk up the growth in plants, secreting new bioactive compounds, as well as enhance biological control activity, decreasing the debris and other wastes that are otherwise harmful to the ecosystem. Putting all these into consideration, endophytic bacteria have exhibited to be a boon, as well as having left good effect on the environment, plants, and also human beings in a number of possible ways.
The other mechanism is a direct one through production of phytohormones, for instance, cytokinin or auxin, Indole acetic acid, and gibberellic acid, or through production of the enzyme amino cyclopropane carboxylate deaminase. Regulators of plant growth secreted by a number of bacteria are signal molecules, which act as chemical messengers, as well as serve a key role as regulators of growth and development in the plant. Among the six pathways for the auxin biosynthesis in bacteria, five are dependent on tryptophan as the primary precursor of IAA. Phosphate solubilizing bacteria, on the other hand, could change insoluble phosphates into forms that are available for absorption by plants through the processes of chelation, acidification, production of gluconic acid, as well as exchange reactions.
Among the major characteristics of plant growth promoting bacteria, is the ability to form plant hormones. This is thought to be part of the mutualistic associations developed between bacteria and plants. These phytohormones change morphology and metabolism of plants, resulting in better absorption of water and minerals, thus healthier and larger plants. For instance, in Chlorellavulgaris, phytohormones result in larger populations of cell. IAA, is a heterocyclic compound, which contains a carboxymethyl group belonging to the family of auxin phytohormone. This group’s phytohormones raise the rate of formation of roots and xylem, control vegetative growth processes, control florescence, tropism, and plants’ fructification. They also have effects on the formation of pigment, photosynthesis, biotic stress factors resistance, and biosynthesis of various metabolites. Gibberelic acids, a diterpenoid acid synthesized by the pathway of terpenoid, are hormones responsible for control of growth, as well as a broad variety of other developmental processes of plants. They enhance division and elongation of cells, though with no inhibitory effects demonstrated by a number of auxins. They, as well participate in the breaking dormancy in germination of seeds. Cytokinins are a category of purine-type phytohormones produced by endophytic bacteria and enhance cell division, morphogenesis of shoot and root, maturation of chloroplast, enlargement of cells, release of auxiliary bud, as well as senescence.