Studies on Non-Symbiotic Diazotrophic Bacterial Populations of Coastal Arable Saline Soils of India

Abstract

The effect of fluctuations of salinity in three different seasons on diazotrophic populations and N 2 fixation in six mono cropped rice field soils of the coastal region of the Gangetic delta of West Bengal, India, was studied. The average pH, ECe, organic carbon and total nitrogen of the soils ranged from 4.99-7.08, 2.02-19.58 dSm -1 , 4.68-12.03 g kgand 0.44-1.70 g kg -1 , respectively. The average log colony forming units of the bacterial populations and N 2 -fixation in the soils varied from 4.61 to 5.86 and 2.74 to 4.52 mg N 2 fixed 50 ml -1 culture media respectively, with the lowest value recorded in summer. Recovery of microorganisms and N 2 -fixation gradually decreased with extraneous addition of NaCl in the culture media. All the eight isolates were Gram positive, spore and capsule formers. They could utilize glucose, sucrose, mannitol, starch, citrate and nitrate, and were catalase and gelatinase positive, but indole, methyl red and Vogues Proskauer reaction negative. The organisms produced alkaline reaction on TSI agar slant. The acetylene reduction assay of the isolates at 0 and 1% NaCl in the culture media were 4.51-164.52 and 1.72-100.6 nmole C 2 H 4 ml -1 culture media in 72 h, respectively. The isolates could fix 2.42-4.45 and 2.04-4.08 mg N 2 fixed 50 ml -1 culture media at 0 and 1% NaCl in the culture media respectively. 16S rDNA sequences of the isolates were similar to the species: Bacillus sp. isolate 28A, Bacillus sp. MOLA 87, Bacillus sp. By113 (B)Ydz-dh, Bacillus sp. PN13, Bacillus licheniformis strain RH101, Bacterium Antarctica 14, Bacillus sp. PN13 and Bacillus megaterium.

Cultivable Nitrogen Fixing Bacteria from Extremely Alkaline-Saline Soils

“…Amphibacillus tropicus, Bacillus arseniciselenatis in solonchak soils and Bacillus spp. in coastal arable saline soils [12] [15]. In mangrove ecosystem other N 2 fixing bacteria have been isolated, e.g.…”

“…Isolation of pure cultures of haloalkaliphilic diazotrophs from several locations in Central Asia and Egypt through micro-oxic enrichments of soils yielded the aerotolerant fermentative haloalkaliphilic bacterium Amphibacillus tropicus and the obligately anaerobic haloalkaliphile Bacillus arseniciselenatis. Apparently, nitrogen fixing activity in alkaline saline soils can be attributed to free-living fermentative low-GC gram-positive bacteria [10] [13]- [15].…”

Osmotolerant Microbial Resources of Saline Ecologies of India: Dynamics and Potential

“…The PGP functions, insecticidal activity and the crystal morphotype of Bt and toxicity of Ps populations were highly variable and independent of the habitat . The Bt population tolerated 5-12 % NaCl and about 98 % other organisms tolerated 3-18 % NaCl .The aerobic heterotrophic and spore forming bacteria were about ten times higher than the anaerobic counterparts Barua et al 2011). In the Gujarat coast also, bacterial guilds were highly diverse, population ranged 8-34 × 10 5 cfu/g soil and 13 bacterial isolates could grow at 2-12 % salt and pH 2-12 (Vora and Modi 2013) and the biosurfactant producing microorganisms of hot springs, ocean, oil wells, petrol pump, desert and costal soils etc.…”

“…However, physico-chemical characters and microbiology have been studied in discrete coastal locations only. The physico-chemical properties of East and West coastal soils of India are highly variable and do not have any relation with soil type (Tripathi et al 2007;Barua et al 2011;Bal et al 2012;Lakshman et al 2013) (Table 11.4). In the two coastal locations viz., Canning (WB) of East coast and Calicut (Kerala) of West coast, the ion balance (me/l) viz., Na 2+ 156 and 320, Ca 2+ 29 and 30, Mg 2+ 120 and 93, Cl − 213 and 354, SO 4 2− 16 and 102, respectively and sodium adsorption ratio (SAR) i.e., 18 and 41, respec- …”

“…The microbial diversity of the East coast and West coast of India viz., Sundarbans coast, Namkhana, Canning, Dhunchi, Kakdweep, Ramaganga, Susunia (WB); CRRI, Chilka, Garakujanga, Bhuiyapada, Ersama (Orissa), Port Blair (AN Islands); Mahe (Puducherry); Calicut (Kerala); Mangalore, Kumta (Karnataka) and Costal Gujarat was studied relatively more thoroughly and observed that they belonged to all known microbial genotypes Ramanathan et al 2008;Barua et al 2011). In the coastal West Bengal, Orissa, Andhra Pradesh, Puducherry and Karnataka, microbial guilds are highly variable and diversity is grossly incoherent of soil physico-chemical constituents.…”