Isolation, Identification and Evaluation of Indigenous Plant Growth Promoting Bacterium Klebsiella pneumoniae PNE1

Abstract

Application of chemical fertilizer is an integral practice to optimize crop productivity, but the dominant use of chemical fertilizers contributes largely to the deterioration of the environment, leads to loss of soil fertility, increases pollution, and causes hazardous diseases. Hence, the chemical fertilizers, pesticides and other supplements are being replaced by the plant growth promoting bacteria (PGPB) due to their improved potency and environment friendly nature. Plant growth-promoting bacteria (PGPB) can enhance plant growth by a wide variety of mechanisms like Phosphate (P) solubilization, Potassium solubilisation, siderophore production, biological nitrogen fixation and Indole acetic acid (IAA) production. The Klebsiella species is also known to exhibit important PGP traits like solubilization of phosphate, phytohormone production and good germination potential. In present study the Klebsiella pneumoniae PNE1 was selected from the isolates obtained from vegetable waste collected from Kadi market. The isolate was selected on the basis of its ability for Nitogen fixation, Phosphate solubilization, Potassium solubilization, IAA production, EPS production and biopolymer degradation. The molecular identification through 16S rRNA gene sequence, confirmed the isolate as Klebsiella pneumonia PNE1. Quantitative analysis of ammonia production revealed that isolate Klebsiella pneumonia PNE1 produced 0.5 µg/ml of ammonia (NH3) on 6th day of incubation and produced 0.09 µg/ml Nitrite after 8th day of incubation. The Phosphate solubilisation Index (SI) of the isolate was 4.16 and the isolate released 177.50 μg/ml Phosphate. The qualitative estimation of Potassium solubilisation by the isolate Klebsiella pneumoniae PNE1 in terms of Potassium solubilisation zone was found to increase gradually from day 1 to 7 days and was maximum at 2nd day with a KSI of 3.6. The isolate Klebsiella pneumoniae PNE1 released 29.94 mg/l Potassium on 21th day of incubation respectively. The IAA production was found to be 94.96 µg/ml. The maximum the EPS yield was 11.3 mg/ml. The Klebsiella pneumonia PNE1 had capacity to degrade Cellulose, Pectin and Xylan i.e. all biopolymers tested. The antibiotic susceptibility test indicated that isolate was sensitive to all 22 antibiotics tested. The Klebsiella pneumonia PNE1 thus, shows important plant growth promoting traits and can be used in a bio-fertilizer formulation for sustainable agriculture.

Enterobacter cloacae PNE2 As Promising Plant Growth Promoting Bacterium, Isolated From The Kadi Vegetable Market Waste, Gujarat.

“…The colonies that grow on Ashby's Mannitol agar are thought to have the potential for nitrogen fixation. The colony was then isolated and purified depending on the distinctive colony morphology for further study 14 .…”

“…The Isolate was identified based on Gram-staining, morphological characteristics, and biochemical test using the HI-Assorted biochemical test kit (KB003) of HI-media Laboratories, Mumbai, India 14 .…”

“…The method involved spreading the 0.1ml of overnight grown culture (set the O.D 0.5 at 540 nm) 21 on a nutrient agar plate and placing antibiotic multidisc on the surface of the plate, incubating the plate at 37±2 °C for 24 hrs. Antibiotic susceptibility test was conducted using combi disk for Gram Negative bacteria from Hi Media Laboratories 14 . The zone of inhibition was measured 22 .…”

“…Approximately 2ml broth was harvested at the interval of 24 hrs. Following the appropriate incubation period, the culture broth was centrifuged for 10 minutes at 10,000 rpm 14 . Nitrite nitrogen production in the broth was examined at an interval of 24 hrs of incubation by standard method 23 .…”

“…Several strains of plant growth promoting bacteria can able to produce exopolysaccharides (EPS). The EPS-producing plant growth promoting bacteria significantly enhance the volume of soil macropores and the rhizosphere soil aggregation, resulting in increased water and fertilizer availability to inoculated plants 14 . Exopolysaccharides can be produced in significant quantities by the bacterial strain Enterobacter cloacae 15 .…”