The role of nitrofixing bakterija Azotobacter spp. i Azospirillium spp. in plant production

U prirodi postoji kružni tok dušika. Iz atmosfera ga usvajaju mikroorganizmi tijekom procesa koji se naziva fiksacija dušika. Biološka fiksacija dušika je proces u kojem posebne skupine mikroorganizama usvajaju plinoviti dušik iz atmosfere i preko enzima nitrogenaze ga reduciaraju do amonijaka. Nesimbiotski fiksatori dušika pripadnici su roda Azotobacter, Azospirillum, Bacillus, Klebsiella. Bakterije roda Azotobacter i Azospirillum imaju važnu ulogu kao nitrofiksatori opskrbljujući biljke dušikom, poboljšavaju rast i razvoj korijena, svojom aktivnošću potiču rast biljaka, povećavaju prinos, proizvode vitamine i enzime, povećavaju usvajanje vode i mineralnih hraniva, utječu na brojnost populacije korisnih mikroba, a i negativno djeluju na fitopatogene gljive. Sadržaj bakterija rodova Azotobacter i Azospirillum, uz celulolitičke mikroorganizme u tlu, predstavlja indikator plodnosti tla. Dobar mikrobiološki sastav tla ne samo da je preduvjet za visoke prinose, nego i za reduciranje mineralne gnojidbe i kemijskih pesticida, a što je s ekonomskog i ekološkog gledišta od iznimnog značaja.There is a circular flow of nitrogen in nature. During a process called nitrogen fixation micro-organisms digest it from the atmosphere. Biological nitrogen fixation is a process in which specific groups of microorganisms adopt gaseous nitrogen from the atmosphere and through the enzyme nitrogenase reduce it to ammonia. Non-symbiotic nitrogen fixation are members of the Azotobacter, Azospirillum, Bacillus, Klebsiella genus. Bacterias of the genusAzotobacter and Azospirillum play an important role as nitrofiksators supplying the plants with nitrogen, improving growth and development of the root and with its activities stimulating plant growth, increasing yield, producing vitamins and enzymes, increasing the adoption of water and mineral nutrients, affecting the population count of beneficial microbes and the negative affect on phytopathogenic fungi. The content of bacterial genus Azotobacter andAzospirillum, with cellulolytic microorganisms in the soil, represents an indicator of soil fertility. Good microbiological composition of the soil is not only a prerequisite for high yields, but also for the reduction of mineral fertilizers and chemical pesticides, what is of the great importance from the economic and environmental point of view