Many crop plants are plagued by fungal root rot. Many saprophytic fungi and bacteria live in the soil and able to inhibit pathogen fungi which would otherwise devastate crop production.

Bacterial populations at a diverse and high level can inhibit the growth of pathagen root fungi.

The general rule is that bacteria are favored by the neutral and low acidity environment and large organic matter resource will favor a diverse and abundant bacteria flora.

The role of minerals is also very interesting as many rot diseases are reduced by optimum Calcium which fortifies plant cell wallls.

The presence of ample soil organic matter leads to an ability to foster nutrient recycling nutrient availability plant defense respones and the diversity and population of soil bacteria.

Compost and compost tea are rich in bacteria. Studies at Oregon state university show the use of compost tea which over a billion colon\y forming unites can largely control damping off disease from Pythium. Specific consoria of bacteria can be developed to stimulate the anabiosis of pathogenic fungi and for their stimulation of plant growth.

Dr Paul Reed Hepperly thank you for your contribution to the discussion

First, we should know the key terms that are include in the question.

01.Bacteria - Are single celled microorganisms that lack a nuclear membrane, are metabolically active and divide by binary fission.

02.Crop productivity -The amount of growth that is attained by a plant within a given period.

03.Decomposing - The process by which dead organic substances are broken down into simpler organic or inorganic matter.

04.Nutrient cycle - The cyclic pathways by which nutrient pass through, in order to be recycled and reutilized.

05.Microbes - Are a living thing that is too small to be seen with the naked eye.

Bacteria are the most important microorganisms. They provide more biological functions. Some of these are,

01.Decomposing of organic matter.

Now a day’s human and macro animal population are rapidly increase (Approximately 140 Million birth per year, Ref; world population prospects 2024). So therefore, the main threats are limitation of the land. When we consider, there are 150,000 peoples are approximately died per day. That is the numerical value of human die. In order there are approximately 4,500,000 peoples are died per month and 54,000,000 peoples are die per year. This is only the numerical number of humans died. When we consider other all animals we cannot imagine how many of are died so. Consider the all died animals and human bodies are not decompose what kind of thing can happen. It causes the limiting of the land that peoples need to live. Therefore, decomposition is very crucial factor to exist in the world. So that kind of thing mainly doing by the bacteria.

02.The role of bioremediation.

Bioremediation is the process of using microorganisms to clean up pollution. In this case some kind of bacteria can break down the harmful pollutants and clean the contaminant soil and the water. So mainly agriculture is not only growing of fish but also rearing of animals. So, when we consider the animals there can be terrestrial and the aquatic animals. Therefore, we have to maintain the soil and water sources.

First, we consider the how-to bacteria involved in to the soil bioremediation. Soil can be polluted because of various things. there are add overdose of chemical fertilizer and the chemical pesticides and weedicides. Using this over more time can accumulate the toxic compound in the soil and it can be very harmful for plant growth and the most of the macro and the microorganisms. And when we consider the yield of that are cultivated plant in this soil, the yield has some toxic compound and it can be harmful for the human health. So therefore, we have to reduce the toxicity level of the soil. So, one of the best methods for that is soil bioremediation using bacteria. This is a broad topic so that I only use some of key point. In hear soil is contaminate with different pollutants. there are and the examples for bio remediation bacteria are,

a) Hydrocarbon contamination - Pseudomonas spp., Bacillus spp.

b) Heavy metal contamination - Achromobacter can use removing heavy metal like cadmium.

c) Pesticide contamination - Sphingomonas

Then we consider the how-to bacteria involve in the water bioremediation. So, when we consider see there can be the sinking of the large size of ship. Due to any reason. The ship has already stored the large amount of fuel. IN any case damage of the fuel tank of the ship this fuel can be leak into the sea. That is the major problem for lining organisms of the water. Due to the oil layer sun light cannot go through the sea water. Due to the lack of sun light and the toxicity the ecosystem of the sea can be degradation. Therefore, we have to remove the oil layer as soon as possible. Removal of fuel layer that are on the sea water is very difficult therefore the easiness way is use bacteria to bioremediation. But this is not a simple process it can be take a long time period. But it is more efficient. So, scientists are producing some specific bacteria for the fuel bioremediation.

Ex; Alcanivorax borkumensis - Key player in marine oil spill cleanup.

(MP Godfrin, M Sihlabela, A Bose, A Tripathi - Langmuir,2018 - ASC Publications)

03. Contribution for the Nutrient regenerating.

Nutrient cycle is one of the important things that happen in the soil. Mainly it is doing by the bacteria and the other animals. In here I am already mention, what is the nutrient cycle. There is another definition. It is a system where energy and matter are transferred between living organism and non-living parts of the organism. When we consider the plant we usually put fertilizer into the soil for the growth of that. In this point, consider most of the added fertilizer are taken up by plants. After some years plant can be die. After dying plant can have considerable amount of nutrients. So that nutrient also important when consider the sustainability. Therefore, we have to reuse that nutrient that are in the dead plant residues. But there is some problem how we regenerate that nutrients. For that Bacteria’s doing major role.

This is not limited only for plant when we consider human they also eat different type of food for get nutrient. After they die that dead bodies also have considerable amount of nutrient. According to the term sustainability that kind of nutrient also we want to regenerated. For that bacteria can doing major role. The process of nutrient regenerate provide adequate nutrient to the soil and increase the fertility of the soil. In present generation most of the human dead bodies are cremating without burial. Burial is the major path for nutrient regenerating within the soil. Now a day’s peoples are moving cremating because of the limitation of the land. But when have land that is -not suitable either living or farming at that stage the most suitable and sustainable way is burial of the dead body. It can improve the fertility of soil after some decade we can rehabilitate that land and then use that for the growing of crop and can get more harvest after better land rehabilitating process. After growing some decade then we can use that land for human habitats.

04. Directly or indirectly stimulate the growth of the plant.

Above we discuss how bacteria indirectly influenced to the stimulate of plant growth. In their how bacteria involve in decomposing of plant and animal matters and how to get nutrient and how to regenerate nutrient. That kind of system (bacteria not directly involve) can also stimulate the plant growth. When we consider direct method, Bacteria can directly stimulate the plant growth. Some plant benificial bacteria promote plant growth directly.

Ex; By making nutrient available to the plant or by stimulating the growth of plant by production of hoemones.

(Clara Pliego, Faina Kamilova, Ben LugtenbergBacteria in agrobiology: crop ecosystems, 295-343, 2011)

Some of bacteria can increase availability of the nutrient and some of bacteria can producing hormone and stimulate the plant growth. When we consider some nutrients that are in the soil is not available to the plant. Because nutrient physical state or chemical state in not suitable for absorption to the plant. Some of the bacteria can change nutrient state and increase the availability of that nutrient.

Ex; Bacillus subtilis can increase phosphate solubilization, potassium solubilization, producing siderophores (Bacillus subtilis produce s siderophores that bind to iron and make it more available to plants.)

Some of bacteria can increase availability of the nutrient and some of bacteria can producing hormone and stimulate the plant growth. When we consider some nutrients that are in the soil is not available to the plant. Because nutrient physical state or chemical state in not suitable for absorption to the plant. Some of the bacteria can change nutrient state and increase the availability of that nutrient. This kind of bacteria we can call as plant growth promoting bacteria (PGPB).

Ex; Bacillus subtilis can increase phosphate solubilization, potassium solubilization, Producing siderophores ( Bacillus subtilis produce s siderophores that bind to iron and make it more available to plants.)

When we consider some of bacteria can produced hormone by itself. that kind of hormone can stimulate the plant growth. It also direct way. According to some of research some of bacteria like,

Pseudomonas,Agrobacterium,Rhizobium, Bradyrhizobiumand Azospirillum

can produce some hormone and that kind of hormone can involve the several stage of plant growth and development such as cell elongation, cell division, Tissue differentiation and epical dominancy. That is the major component of the plant growth and development. As a example for that kind of hormone and the producing bacteria is Pseudomonas and Agrobacterium produce indole-3-acetic acid via the indole-3-acetamide pathway for which genes are plasmid born.

(Antonia Costacurta, Jos Vanderleyden Critical reviews in microbiology 21 (1), 1-18, 1995)

Another book shows that Azotobacter chroococcum, Bacillus megaterium, Bacillus mucilaginosus were found to be able to synthesize cytokinin (CKs) and indolyl acetic acid (IAA)

(MG Sokolova, GP Akimova, OB VaishlyaApplied Biochemistry and Microbiology 47, 274-278, 2011).

cytokinin can increase promotion of cell division, Shoot and root development, Delay of leaf senescence, Seed germination, Regulation of stomatal function.

IAA(indolyl acetic acid) can increase cell elongation and growth, Root development, Flowering and bud dormancy, Tropisms like things. That like method can stimulate the plant growth and increase the crop yield and the crop productivity. Above mention hormone we can get from shop but it is two high but, in some situation, we have to buy that kind of the hormone. In some cases, like increase the root development we can inoculant bacteria that are producing plant hormone in the soil. This is the most sustainable way. In conclusion of this part is when provide optimum condition for suitable bacteria can improve the soil quality also crop productivity.

05. Contribution for Nutrient cycle.

Consider nutrient it is one of major function of the ecosystem. There are many nutrient cycles we can identify within this ecosystem. Examples are carbon cycle, Nitrogen cycle, Phosphorous cycle like. when we consider nitrogen cycle There are few steps that are,

a) Nitrogen fixation. (Atmospheric nitrogen converts in to ammonia using Rhizobium bacteria.)

b) Nitrification. (Ammonia convert into nitrites using Nitrosomonas and nitrites convert into nitrate using Nitrobacter)

c) Assimilation.

d) Ammonification (decomposition)

e) Denitrification. (Nitrate again convert in to the Nitrogen gas and released in to the atmosphere.)

That is the step that are in the nitrogen cycle. So therefore, bacteria can mainly contribute to the nutrient cycle.

Now a day’s world population is rapidly increase and increasing the demand for the food and increasing the demand for the land. But crucial thing is food and the land have been limiting for past few years. So that mitigate that limitation and for increase the crop productivity we have to follow some alternative things. Using bacteria is the one of major thing. It can improve the soil fertility and contribute to the nutrient cycle and increase the overall crop productivity and can fulfill the demand.

Dr Vidoosha Sandeepa thank you for your contribution to the discussion