Growth of Azospirillum brasilense Cd in the presence of different NaCl
concentrations showed that it tolerates up to 200 mM NaCl in the medi
um, without appreciable decline in growth rate. At 300 mM NaCl, a decr
ease of 66% in growth was observed at 24 h of culture. At 48 h of cult
ure, bacteria in the presence of 300 mM NaCl reached the maximum optic
al density value that was attained at 12 h by control cultures. This i
nvestigation was designed to elucidate the effect of saline stress on
Azospirillum brasilense Cd and the physiologic mechanism involved in i
ts possible salinity tolerance. For this reason, studies of other osmo
lytes, as well as of putrescine metabolism and protein patterns were d
one with bacteria grown with this NaCl concentration in the medium, at
24 and at 48 hours. A. brasilense responded to saline stress elevatin
g the intracellular concentration of glutamate at 24 h, and of K+ at 4
8 h. Glucan pattern, putrescine metabolism, and total and periplasmic
protein patterns of the treated group showed several changes with resp
ect to the control. In spite of the several cellular functions affecte
d by saline stress, the results imply that A. brasilense Cd shows sali
nity tolerance in these experimental conditions.