Pink-pigmented Methylotrophic Bacteria Research Articles

Epiphytic pink-pigmented methylotrophic bacteria enhance germination and seedling growth of wheat (Triticum aestivum) by producing phytohormone

Methylotrophic bacteria were isolated from the phyllosphere of different crop plants such as sugarcane, pigeonpea, mustard, potato and radish. The methylotrophic isolates were differentiated based on growth characteristics and colony morphology on methanol supplemented ammonium mineral salts medium. Amplification of the mxaF gene helped in the identification of the methylotrophic isolates as belonging to the genus Methylobacterium. Cell-free culture filtrates of these strains enhanced seed germination of wheat (Triticum aestivum) with highest values of 98.3% observed using Methylobacterium sp. (NC4). Highest values of seedling length and vigour were recorded with Methylobacterium sp. (NC28). HPLC analysis of production by bacterial strains ranged from 1.09 to 9.89μgml(-1) of cytokinins in the culture filtrate. Such cytokinin producing beneficial methylotrophs can be useful in developing bio-inoculants through co-inoculation of pink-pigmented facultative methylotrophs with other compatible bacterial strains, for improving plant growth and productivity, in an environment-friendly manner.

Effects of Methylobacterium spp. strains on rice Oryza sativa L. callus induction, plantlet regeneration, and seedlings growthin vitro1

Maliti, C. M. (Department of Biology & Med. Lab. Technology, Bronx Comm. College, CUNY, University Avenue & West 181 Street, Bronx, NY 10453), D. V. Basile (Department of Biological Sciences, Lehman College, CUNY, Bronx, NY 10468), and W. A. Corpe (Department of Biological Sciences, Columbia University, New York, NY 10027). Effects of methylobacterium spp. strains on rice Oryza sativa callus induction, plantlet regeneration and seedlings growth in vitro. J. Torrey Bot. Soc. 132: 355–367. 2005.—Leaf surfaces of higher plants are colonized by diverse microorganisms. In the present study we report the isolation two strains of pink-pigmented methylotrophic bacteria (PPFM) designated Q4 & Q5. Both strains significantly stimulated growth and development of two rice cultivars, Japonica cv. CR76 and Indica cv. A301, cultured axenically on MS or B5 medium. Co-incubation of strains Q4 and Q5 with embryo-derived rice calli on B5 medium-devoid of exogenous phytohormones resulted in continued callus growth but inhibited plantlet regeneration. These results mimicked those produced by B5 medium supplemented with auxin and cytokinin. Co-culture of Q4 & Q5 as cobionts with 5 day old Japonica and Indica seedlings resulted in a significant (P ≤ 0.05) stimulation of four growth parameters; root development, stem growth, leaf development and biomass productivity, measured in 9 day growth period. The results of the in vitro experiments indicate that strain Q4 and /or Q5 inhabiting rice plant surfaces under cultivation could significantly stimulate the plants growth and development.

Plant colonization by pink-pigmented facultative methylotrophic bacteria (PPFMs)

Bacteria belonging to the genus Methylobacterium are characterized by being able to rely on methanol as a sole carbon and energy source and by presenting a more or less intense pink reddish pigmentation. These bacteria, also referred to as pink-pigmented methylotrophic bacteria (PPFMs), are common inhabitants of the phyllosphere and are found in many other environmental samples. Since they grow slowly they are often overlooked and their impact on phyllosphere microbial communities and on the plants harboring them is not well studied nor has their ecology been elucidated. In a survey of PPFM colonization in three different agricultural sites, PPFM populations were identified on both red clover and winter wheat, but red clover was more consistently colonized. Isolations from collected leaves showed PPFM populations to decrease from spring towards summer, but they increased again towards the end of the cropping season. Isolates from red clover readily colonized winter wheat leaves and vice versa in greenhouse experiments, but population sizes were dependent on the application procedure. Tested isolates had also good potential to colonize the rhizosphere, especially after seed inoculations. Confocal scanning laser microscopy showed gfp-tagged isolates to colonize the surface of clover leaves by forming large aggregates.

Electroporation of Pink-Pigmented methylotrophic bacteria

Electroporation conditions were determined for electroporating the broad-host-range plasmid pHX200V-47-ml (22.4 kb) into four pink-pigmented methylotrophic strains (Methylophilus methylotrophus AS1,Methylobacterium extorquens AM1,Methylobacterium organophilum XX, andPseudomonas sp. M27). For these methylotrophs, a high electric-field strength (15 kV/cm) and high DNA concentration (18.75 ng/μI competent cells) were necessary to produce plasmid-containing cells. The addition of 30% polyethylene glycol (PEG) to the electrocompetent cells resulted in a five-to six-fold increase in electroporation efficiency in strainsM. methylotrophus AS1, M.extorquens AM1, andM. organophilum XX, and also allowed successful electroporation ofPseudomonas sp. M27 (no electroporants were obtained without PEG). The maximum electroporation efficiencies for M.methylotrophus AS1, M.extorquens AM1, M.organophilum XX, andPseudomonas sp. M27 were 1.31 X 103, 2.57 X 103, 5.25 x 103, and 1.2 x 104 electroporants/(μg DNA, respectively). This, along with our previous article (1), are the first reports of a plasmid being successfully electroporated into these strains.

Prevention of pink-pigmented methylotrophic bacteria ( Methylobacterium mesophilicum ) contamination of plant tissue cultures

Prevention of pink-pigmented methylotrophic bacteria ( Methylobacterium mesophilicum ) contamination of plant tissue cultures

Prevention of pink-pigmented methylotrophic bacteria (Methylohacterium mesophilicum) contamination of plant tissue cultures

Pink-pigmented facultative methylotrophic bacteria (PPFMs) have been found on the surfaces of leaves of most plants tested. We found PPFMs on the leaf surfaces of all 40 plants (38 species) tested and on soybean pods by pressing onto AMS medium with methanol as the sole carbon source. The abundance ranged from 0.5 colony forming unit (cfu) /cm(2) to 69.4 cfu/cm(2) on the leaf surfaces. PPFMs were found in homogenized leaf tissues of only 4 of the species after surface disinfestation with 1.05% sodium hypochlorite and were rarely found in cultures initiated from surface disinfested Datura innoxia leaves or inside surface disinfested soybean pods. Of 20 antibiotics tested for PPFM growth inhibition, rifampicin was the most effective and of seven others which also inhibited PPFM growth, cefotaxime should be the most useful due to the expected low plant cell toxicity. These antibiotics could be used in concert with common surface sterilization procedures to prevent the introduction or to eliminate PPFM bacteria in tissue cultures. Thus, while PPFMs are present on the surfaces of most plant tissues, surface disinfestation alone can effectively remove them so that uncontaminated tissue cultures can be initiated in most cases.