Abstract
Phosphate solubilizing and nitrogen-fixing bacteria have a vital role in improving soil fertility and reverting adversely affected soil properties. These bacteria could contribute towards sustainable agriculture with a focus on reducing excessive use of commercial fertilizers. This study aimed at investigating autochthonous populations of phosphate solubilizing and nitrogen-fixing bacteria from Lake Ol’Bolossat sediments. The total microbial counts ranged between 4.8 x 103 to 8.5 x 105 cfu/ml. A total of 50 bacteria were isolated, 34 were obtained from Pikovskaya’s agar medium while 16 were obtained from Norris Glucose Nitrogen free medium. Based on morphological and 16S rRNA gene analyses, the isolates were clustered under the genera Bacillus, Arthrobacter, Pseudomonas, Paenibacillus, Fictibacillus and Acinetobacter. Among potentially novel strains, four strains NFDA2, PKGBC1 (MT799539), PKGB5 and SCEC2 (MT799543) belonged to genus Bacillus, three strains NFGA1 (MT799529), NFGA4 and SCDB3 belonged to the genus Pseudomonas, two strains NFEB6 (MT799528) and NFDC5 belonged to the genus Paenibacillus, one strain PKHC3 (MT7995441) belonged to the genus Arthrobacter while one strain NFDC4, belonged to the genus Acinetobacter. Generally, the phosphate solubilizing bacteria were the most diverse and genera Bacillus, Fictibacillus and Pseudomonas were the most dominant, however, nitrogen-fixing bacteria were dominated by genera Arthrobacter and Pseudomonas.
Highlights
Rapid growth in industrialization along with the increasing population has led to the increase in the demand for crops (Chennappa et al, 2019) which further increases the pressure on the use of land, water and nutrients to increase crop yields
The highest microbial counts were recorded at 0-30 cm depth for all sampling points, the results showed microbial counts decreased with increase in depth, notably at the depth of 0-30 cm, 30-60 cm and 60-90 cm, for example, phosphate solubilizing bacteria counts ranged between 2.7 x 103 to 7.4 x 105 cfu/ml, nitrogen-fixing bacteria counts were 1.9 x 103 to 4.6 x 105 cfu/ml while total microbial counts ranged between 4.8 x 103 to 8.5 x 105 cfu/ml (Figure 3)
The phosphate solubilizing bacteria (PSB) and nitrogen-fixing bacteria (NFB) counts were in line with Stankevica et al (2015) who showed that freshwater sediments are highly populated with microorganisms ranging between 5.2 x 103 to 6.9 x 106 cfu/g of dry matter
Summary
Rapid growth in industrialization along with the increasing population has led to the increase in the demand for crops (Chennappa et al, 2019) which further increases the pressure on the use of land, water and nutrients to increase crop yields. Phosphorous, and potassium (NPK) are primary nutrient components in commercial fertilizers that play an important role in plant nutrition Overreliance on these commercial nutrients, have a direct effect on soil microbiological aspects, environmental pollution, and health hazards on reaching the soil in significant quantities (Çakmakçi et al, 2006). These results to alterations in the soil microbial composition, soil fertility and crop productivity; altering soil nitrogen balance, interfering with ammonification, and hindering mycorrhizal symbiosis or nodulation in plants, as well as plant growth, soil structure, organic matter decomposition, and nutrients recycling (Chennappa et al, 2019). A recent study by Kaminsky et al (2018) showed that excessive fertilization of inorganic phosphorous change microbiome composition affecting plant growth
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