Nodule bacteria are symbiotic organisms that fix nitrogen

Nodule bacteria are microorganisms that belong to the genus Rhizobium (literally from the Greek - "living on the roots"). They are introduced into the root system of the plant and live there. In this case, they are not parasites, because not only bacteria, but the representative of the flora also benefits. Such a mutually beneficial existence of organisms is called symbiosis. In this case, plants additionally receive atmospheric nitrogen, which "catch" microorganisms, and the bacteria themselves - carbohydrates and minerals. There is an opinion that these prokaryotes settle in the roots of only representatives of the legume family, but this is not so. There are other plants, the roots of which serve as the habitat for nodule prokaryotes - for example, alder, reed forest, etc.

For organisms of the genus Rhizobium, polymorphism is characteristic, that is, the forms of bacteria are very diverse. These microorganisms can be mobile and immobile, have the form of cocca or rods, filamentous, oval. Most often young prokaryotes have a rod-shaped shape, which with growth and age changes due to the accumulation of nutrients and immobilization. In its life cycle, the microorganism passes through several stages, which can be judged by its appearance. Initially, it is a form of a wand, then a so-called "belted wand" (it has belts with fatty inclusions), and finally a bacterioth is a large immobile cell of irregular shape.

Nodule bacteria possess specificity, that is, they are able to settle only in A certain group or plant species. This property in microorganisms was formed genetically. Also important is the efficiency - the ability to store atmospheric nitrogen in sufficient quantities for its host plant. This property is not permanent and may vary due to habitat conditions.

About how the nodule bacteria fall into the root, there is no consensus, but there are a number of hypotheses about the mechanism of their penetration. So, some scientists believe that prokaryotes are implanted into the root through the damage to their tissues, while others say of penetration through the root hairs. There is also an auxin hypothesis - the assumption of satellite cells that help bacteria to penetrate into the root cells.

The very introduction occurs in two phases: first - infection of the root hairs, then - the formation of nodules. The duration of the phases is different and depends on the specific plant species.

The importance of bacteria that are able to fix nitrogen is great for agriculture, since these organisms can increase yields. From these microorganisms, a bacterial fertilizer is prepared, which is used to treat seeds of legumes, which contributes to faster infection of the roots. Different species of the family butterflies during planting even on poor soils do not require additional nitrogen fertilization. So, 1 hectare of legumes "in work" with nodule bacteria during the year translates into a bound state of 100-400 kg of nitrogen.

Thus, nodule bacteria are symbiotic organisms that are very important not only in plant life, but also in the cycle of nitrogen in nature.