Answer: a. True.
Explanation:
<em>Lactobacillus </em>is a genus of gram-positive, facultative or microaerophilic bacteria that produce lactic acid. <u>They are normally found in different parts of the body such as the mouth, digestive tract and vagina</u>. Lactobacilli usually do not cause disease, although they can cause dental caries. Some lactobacilli have a homofermentative metabolism, that is, they produce lactic acid from sugars, which makes their environment acidic and inhibits the growth of pathogenic bacteria. Some species of Lactobacillus are used in the industry for the production of yogurt, cheese and other fermented foods.
<em>Escherichia coli</em> is a bacterium that is part of the microbiota of the gastrointestinal tract of various animals. It is a gram-negative bacillus, facultative anaerobe, and the most abundant commensal of the microbiota of the gastrointestinal tract where, together with other microorganisms, it is essential for the correct functioning of the digestive process. It also participates in the production of B and K vitamins.
<em>Rhizobium </em>is a genus of gram-negative soil bacteria that fix atmospheric nitrogen and live in symbiosis with certain plants (such as leguminous plants) in their roots, after a process of infection induced by the plant itself through the secretion of lectin, to which they provide the nitrogen necessary for the plant to live and which in return gives it shelter. Fixation is the combination of molecular nitrogen (N2) with hydrogen or oxygen to give ammonium or oxides that are incorporated into the biosphere. Molecular nitrogen, which is the major component of the atmosphere, is inert and not directly usable by most living things. Therefore, it involves the incorporation of a significant amount of nitrogen into the biosphere.
<u>Therefore, all three are considered beneficial</u>.
