Salt tolerance of diazotroph Alaligenes faecalis and its salt-tolerant association with host rice

Abstract

There are about 20 million hectares of saline land in North and East China, which causes a loss of approximately 30 million tons of crop yield annually. Some studies conducted in China showed that biofertilizer containing salt-tolerant nitrogen-fixing bacteria could promote growth of plants and increase the yield of crops (Ping et al., 1996). Alcaligenes faecalis A1501, which was isolated from paddy soils in South China in 1980, could grow well in solid or liquid medium containing 0.8 mol/L NaCl

Table 1 Effect of various concentrations of NaCl on growth of A. faecalis frown in solid medium

. Growth of bacteria was repressed in solid medium containing 1.2 mol/L NaCl. A1501 could grow very slowly even if the NaCl concentration reached 1.6 mol/L in liquid medium. A1501 could produce IAA under salt stress and maintain N-fixing activity until the NaCl concentration was higher than 1.0 mol/L

Table 2 Identification of IAA produced by A. faecalis A1501 under salt street (0.4 M NaCl)

Table 3 Associative nitrogen fixation between host rice and A. faecalis A1501

. Southern hybridization of total DNA from A1501 grown under condition of different NaCl concentration with Klebsiella pneumoniae nifHDK DNA probe show that homologous hybridization bands under the normal condition were identifical to those of the cells grown under the salt stress.