Ochrobactrum, bacillus and Enterobacter isolates of Hot Water Spring Augment the Growth of Zea Mays Seedlings

Abstract

Hot springs situated at high altitudes is a kind of remarkable ecosystem for the exploration of microbial flora. It was hypothesized that hot springs can harbor bacteria with plant growthpromoting and exopolysaccharides (EPS) producing ability that can favour the growth of plants. For the investigation of this hypothesis, seven EPS producing bacterial isolates were isolated from a water sample of hot water spring of Tattapani, Azad Kashmir and characterized morphologically and biochemically. Three out of seven isolates (BE1, BN1 and BN3) showed significant production of EPS (14-15 mg / 100 ml). Growth kinetics study revealed that optimum EPS production was attained at pH 9, with fructose as a carbon source and peptone as a nitrogen source. Inoculation of these isolates caused augmentation in seed germination (27-38 %), shoot length (27-35 %), seedling length (10-14 %), number of roots (12-25 %) of Zea mays (variety-MMRI yellow) seedlings and significant rise in auxin (28-51 %) and soluble protein content (50-68 %) as compared to non-inoculated treatment. Alcian blue staining unveiled the good colonization potential of these isolates on inoculated roots. Bacterial isolates were identified as Ochrobactrum intermedium (BE1), Bacillus pumilus (BN1) and Enterobacter cloacae (BN3), respectively through 16S rRNA analysis. Bacterial strain BN3 showed promising results for plant growth promotion along with EPS production. Fourier-transform infrared (FTIR) spectroscopy of EPS produced by strain BN3 revealed the complex composition of EPS. We concluded that hot springs can be the possible home for EPS producing bacteria with plant growth promotion capability.

Keywords

• exopolysaccharides
• fourier-transform infrared spectroscopy. hot spring
• plant growth promotion
• zea mays.