azotobacter is the bacteria that helps nitrogen fixation in the soil.
azotobacter is the bacteria that helps nitrogen fixation in the soil.
which bacteria helps nitrogen fixation in the soil?
azotobacter
nitrogen fixation is carried out naturally in the soil by a wide range of microorganisms termed diazotrophs that include bacteria such as "azotobacter", and archaea. some nitrogen-fixing bacteria have symbiotic relationships with some plant groups, especially legumes. looser non-symbiotic relationships between diazotrophs and plants are often referred to as associative, as seen in nitrogen fixation on rice roots. nitrogen fixation also occurs between some termites and fungi. it also occurs naturally in the air by means of nox production by lightning.
nitrogen fixation
diazotrophic cyanobacteria have evolved a number of mechanisms to ensure that oxygen doesn’t interfere with the oxygen-sensitive enzyme complex responsible for nitrogen fixation, since these enzymes are sensitive to oxygen. oxygen is especially toxic to nitrogenase. one way in which nitrogen-fixing cyanobacteria, such as those in the genera "nostoc" and "anabaena", avoid oxygen toxicity is through specialized cells called heterocysts that lack photosystem ii and hence do not have oxygen evolution. as a diazotrophic cyanobacterium that has oxygen-evolving photosystem ii, one of the ways by which "crocosphaera watsonii" protects its nitrogenase from oxygen is through the adaptation of a diel rhythm. this temporally separates carbon and nitrogen metabolism between day and night, respectively. since an array of enzymes are involved in the regulation of carbon and nitrogen metabolism, this separation entails temporal regulation of many enzymes and processes in these bacteria. consistent with this, many genes involved in nitrogen fixation and photosynthesis show variation in transcription between day and night. this difference in gene expression between light and dark periods for genes involved in nitrogen fixation was about ten times bigger than for genes involved in photosynthesis, suggesting more stable photosystems compared to nitrogenase in these bacteria. the expression of many genes involved in nitrogen fixation and photosynthesis have been individually monitored. these include genes encoding the proteins nifh, nifx, glutamate synthetase, ntca, glnb-like proteins and glgp, all of which have essential roles in nitrogen fixation. the expression of all these genes were at their peak at the beginning of dark period and were at their minimum in the early light period. furthermore, genes encoding for photosynthetic proteins such as photosystem i subunit vii (psac), the photosystem ii d1 protein (psba1) and the photosystem ii oxygen-evolving complex protein (psbo), and glga showed diel variation in expression, with the highest and lowest expression at daytime and nighttime, respectively. about 30% of the genome of "crocosphaera watsonii" showed diel variation in expression, indicating its importance. all of these patterns indicate a temporal separation of photosynthesis and nitrogen fixation in "crocosphaera watsonii."
crocosphaera watsonii