Question

Bio-fertilizers include:
A. Nitrogen fixing bacteria
B. Nitrogen fixing cyanobacteria
C. Both bacteria and cyanobacteria
D. Bacteria, cyanobacteria and mycorrhizal fungi

Answer 1

A bio-fertilizer is a substance which contains living microorganisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizo-sphere or the inside of the plant and promotes growth by increasing the availability or availability of primary nutrients to the host plant.

Complete answer:
The term biofertilizers or microbial inoculants could also be used to include all organic resources (manure) for plant growth which are rendered in an available form for plant absorption through microorganisms or plant associations or interactions. Bio-fertilizers are of the three types which are the nitrogen fixing bacteria, nitrogen fixing cyanobacteria and mycorrhiza.
So, the right answer is option D.
Plant growth is very hooked into the bacteria, saprophytic, and the mycorrhizal fungi which facilitates the cycling and the mobilization of nutrients. Over 95% of the sulfur (S) in the soil is present in an organic form. Sulfate-esters and sulfonates, the two most kinds of organo-S in soils, arise through deposition of biological material and are transformed through subsequent humification.
Fungi and bacteria release sulphur from sulfate-esters using sulfatases, however, release of S from sulfonates is catalyzed by a bacterium of the multi-component mono-oxygenase system. The S gene is employed as a key marker during this desulfonation process to review sulfatase activity in soil bacteria identified as Variovorax , Polaromonas , Acidovorax , and Rhodococcus.

Note:
The rhizosphere is considered a hot spot for microbial activity and up to date studies indicate that this is often also the case for the mycorrhizosphere where bacteria may attach to the fungal hyphae capable of mobilizing organo-S.