Abstract
BackgroundNight-soil compost (NSC) has traditionally been conserving water and a source of organic manure in northwestern Himalaya. Lately, this traditional method is declining due to modernization, its unhygienic conditions, and social apprehensions. Reduction in the age-old traditional practice has led to excessive chemical fertilizers and water shortage in the eco-sensitive region. In the current study, a bacterium has been analyzed for its safety, cold-adaptation, efficient degradation, and plant growth-promoting (PGP) attributes for its possible application as a safe bioinoculant in psychrotrophic bacterial consortia for improved night-soil composting.ResultsGlutamicibacter arilaitensis LJH19, a psychrotrophic bacterium, was isolated from the NSC of Lahaul valley in northwestern Himalaya. The strain exhibited amylase (186.76 ± 19.28 U/mg), cellulase (21.85 ± 0.7 U/mg), and xylanase (11.31 ± 0.51 U/mg) activities at 10 °C. Possessing efficient hydrolytic activities at low-temperature garners the capability of efficient composting to LJH19. Additionally, the strain possessed multiple PGP traits such as indole acetic acid production (166.11 ± 5.7 μg/ml), siderophore production (85.72 ± 1.06% psu), and phosphate solubilization (44.76 ± 1.5 μg/ml). Enhanced germination index and germination rate of pea seeds under the LJH19 inoculation further supported the bacterium’s PGP potential. Whole-genome sequencing (3,602,821 bps) and genome mining endorsed the cold adaptation, degradation of polysaccharides, and PGP traits of LJH19. Biosynthetic gene clusters for type III polyketide synthase (PKS), terpene, and siderophore supplemented the endorsement of LJH19 as a potential PGP bacterium. Comparative genomics within the genus revealed 217 unique genes specific to hydrolytic and PGP activity.ConclusionThe physiological and genomic evidence promotes LJH19 as a potentially safe bio-inoculant to formulate psychrotrophic bacterial consortia for accelerated degradation and improved night-soil compost.
Highlights
Night-soil compost (NSC) has traditionally been conserving water and a source of organic manure in northwestern Himalaya
Physico-chemical properties of night-soil compost (NSC) samples and bacterial characterization The compost samples were collected from the compost pile randomly in triplicate from the collection chamber of the traditional dry toilet ‘ghop’ (Fig. 1a)
The compost sample was obtained from the core of the pile; the temperature, pH, and electrical conductivity (EC) of the collected samples were 9.9 °C, 10, and 1674 μS, respectively
Summary
Night-soil compost (NSC) has traditionally been conserving water and a source of organic manure in northwestern Himalaya. This traditional method is declining due to modernization, its unhygienic conditions, and social apprehensions. To meet the high demand for manure and water shortage during winter, the traditional method of composting human excreta (night-soil) using dry toilets is prevalent in this region [2,3,4]. The dry toilet consists of a defaecation room (upper storey) and a collection chamber (lower storey) (Fig. 1a). Promotion of the safe and hygienic winter dry toilets aided with scientific intervention is necessary to sustain the agro-ecosystem and conservation of water in such highland areas
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