Microbial cells accumulate pigments under certain culture conditions, which have very important industrial applications. Microorganisms can serve as sources of carotenoids, the most widespread group of naturally occurring pigments. More than 750 structurally different yellow, orange, and red colored molecules are found in both eukaryotes and prokaryotes with an estimated market of $ 919 million by 2015. Carotenoids protect cells against photooxidative damage and hence found important applications in environment, food and nutrition, disease control, and as potent antimicrobial agents. In addition to many research advances, this paper reviews concerns with recent evaluations, applications of microbial pigments, and recommendations for future researches with an understanding of evolution and biosynthetic pathways along with other relevant aspects.

The combined inoculation of two or more microbial species, such as phosphate-solubilizing bacteria (PSB) and arbuscular mycorrhizal fungus (AMF) and PSB and nitrogen fixers, has often been reported to exert positive effect on growth and yield of various crops; however, reports on dual inoculation of PSB and free-living phosphate-solubilizing fungi (PSF) are hardly available, which makes this study relevant. P-solubilization efficiency (SE) was highest for Bacillus sp.; SE values for RM-2 were highest on the 2 nd day of inoculation, whereas those for Aspergillus niger S-36 continuously increased up to the 5 th day of incubation. We performed an experiment to evaluate the co-inoculation effect of two phosphate-solubilization-efficient strains of bacteria and fungi in a pot trial. RM-2 strain produced chitinase that might have conferred biocontrol properties on chickpea. The overall growth of plants via dual inoculation was significantly (P = 0.05) greater than that for control and single inoculations in a pot trial, indicating the positive synergistic effect of co-inoculation of PSB and PSF for crop improvement, which could be useful for farmers and sustainable agriculture.

The selection of strains for production of biofertilizers is of primary importance. A strain with diverse growth promoting activities, especially the nitrogen fixation and phosphate solubilization, has highest preference over those with just one activity. In the present study, a symbiotic nitrogen fixing bacterium was isolated from the root nodules of chickpea and characterized as Ochrobactrum intermedium CP‐2 on the basis of biochemical tests and partial 16S rRNA gene sequencing and blast analysis. Besides fixing nitrogen, the CP‐2 strain also showed the ability of phosphate solubilization and indole acetic acid production. It was also found positive for ammonia and siderophore production. A significant increase in the lengths of radical and plumule and percent germination was observed when the rhizobacterial strain selected for the study was inoculated in vitro for seed assay. O. intermedium CP‐2 significantly (p < 0.05) increased shoot and root lengths, fresh and dry weights, and yield of mung bean plants both in pot trials and under field conditions. The nutrient uptake and microbial count also increased significantly with inoculation of the strain during the experiment. This study revealed the positive effect of O. intermedium CP‐2 on mung bean crop.