Beijerinckia derxii releases plant growth regulators and amino acids in synthetic media independent of nitrogenase activity.
OBJECTIVE
This study aims at evaluating the ability of Beijerinckia derxii, a free-living nitrogen (N)-fixing bacterium frequently isolated from tropical soils, to release certain plant growth regulators [indoleacetic acid (IAA), ethylene, polyamines] and amino acids into the growth medium.


RESULTS
The production of those substances was compared using both cultures in which nitrogenase was active (N-free medium) and cultures in which nitrogenase was repressed (combined-N cultures). Those cultures were grown under agitation and in absence of agitation. Total IAA production was higher in agitated, N-free cultures but specific production was greater in combined-N cultures under agitation. Putrescine and spermidine were detected under all conditions tested. Ethylene was produced in both N-free and combined-N cultures. A greatest diversity of amino acids was released in N-free cultures.


CONCLUSIONS
There was no inhibition of the production of the analysed substances under conditions where nitrogenase was inactive.


CONCLUSIONS
Beijerinckia derxii is potentially a producer of plant-active substances; its presence in the natural environment suggests that this bacterium may contribute to the development of other living organisms.
Thuler
D S
DS
Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, Brasil.
Floh
E I S
EI
Handro
W
W
Barbosa
H R
HR
D000596:Amino Acids / Q000378:metabolism*; D042062:Beijerinckiaceae / Q000378:metabolism*; D003470:Culture Media; D005030:Ethylenes / Q000096:biosynthesis; D007210:Indoleacetic Acids / Q000378:metabolism; D009591:Nitrogenase / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D011073:Polyamines / Q000378:metabolism; D011700:Putrescine / Q000032:analysis; D012988:Soil Microbiology; D013095:Spermidine / Q000032:analysis
D000596:Amino Acids; D003470:Culture Media; D005030:Ethylenes; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D011073:Polyamines; C030737:indoleacetic acid; C036216:ethylene; D009591:Nitrogenase; D013095:Spermidine; D011700:Putrescine