In the present investigation, five strains of Janthinobacterium obtained from Rohtang Pass, Himachal Pradesh, India along with one strain of Bacillus decolorationis (IARI-SL-13) were screened qualitatively and quantitatively for their ability to solubilize K at different temperatures ranging from 5 to 30 °C. All the selected strains do not produce violet colonies, instead produced pink or red coloured colonies. In a plate assay, among all the strains tested, Janthinobacterium sp. IARI-R-81 was most efficient in solubilization of K at lower temperatures of 5 and 10 °C and was closely followed by Janthinobacterium lividum (IARI-R-71). Janthinobacterium sp. IARI-R-70 did not produce any detectable halo zones at all temperatures except 10 and 25 °C. Quantitative analysis revealed that all the selected pigment-producing strains could solubilize potassium-bearing mineral at low temperature (5 °C). J. lividum IARI-R-50 strain was most efficient in solubilizing K (29.87 ± 1.22 µg K/mL) from its mineral at 5 °C. This strain was typical as it solubilized almost the same amount of K both at 5 and 30 °C indicating its capability to adapt to different temperatures. All other strains showed a significantly higher concentration of solubilized K at 30 °C as compared to other temperatures tested. The non-pigmented B. decolorationis showed solubilization only at 25 and 30 °C and the concentration of K solubilized at 30 °C was significantly higher than at 25 °C. There was no correlation between pigment production and solubilization of potassium. This is the first report depicting solubilization trait of members of genus Janthinobacterium and confirms its evolutionary relatedness to Collimonads.
Keywords: 16S rRNA gene sequencing; Genus Janthinobacterium; Mineral weathering potential; Pigment analysis.