Submitted to: DNA and Cell Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/30/2010
Publication Date: 7/13/2010
Citation: Schloss, P.D., Allen, H.K., Klimowicz, A.K., Mlot, C., Gross, J.A., Savengsuksa, S., Mcellin, J., Clardy, J., Ruess, R.W., Handelsman, J. 2010. Psychrotrophic Strain of Janthinobacterium lividum from a Cold Alaskan Soil Produces Prodigiosin. DNA and Cell Biology. 29(9):533-541. Interpretive Summary: Soil microbial communities are some of the richest on earth because of their abundance and diversity. For this reason, soil is an excellent resource in the search for microbial natural products. Culturing bacteria from soil has led to major discoveries, such as the antibiotic streptomycin, and combining culturing with culture-independent methods will be a powerful approach to expanding our understanding of microbial diversity. Previous culture-independent studies of a remote, Alaskan soil are complemented here by a culture-dependent analysis of this cold environment. A collection of Alaskan soil bacterial isolates was screened for the production of compounds that inhibited the growth of Bacillus subtilis or Pseudomonas putida, yielding a red-pigmented strain of Janthinobacterium lividum (strain BR01) that produced the pigment prodigiosin at cool temperatures. The diversity of J. lividum in this environment was studied further, revealing a purple, violacein-producing strain of J. lividum (strain BP01), which is the previously known pigmentation of J. lividum. Both strains were shown to be resistant to beta-lactam antibiotics. J. lividum BR01 is the first example of prodigiosin production in a betaproteobacterium, and the genes encoding prodigiosin production differ from those found in a known producer, Serratia. sp. Both J. lividum BR01 and BP01 have identical 16S rRNA gene sequences to previously reported strains of J. lividum; therefore culturing alone revealed the vast phenotypic diversity within the J. lividum species. The results show that the characterization of culture collections from novel environments continues to be a productive means of discovering and deciphering microbial diversity.
Technical Abstract: In the search for useful natural products such as enzymes and antibiotics, soil continues to be a fruitful environment. Combining culture-dependent and -independent approaches will accelerate discovery from environments as microbially complex as soil. Here we complement previous culture-independent analyses of a non-permafrost, cold Alaskan soil by constructing a collection of bacteria cultured from this soil. This collection was analyzed by 16S rRNA sequencing and screened for antibiosis, yielding a red-pigmented strain of Janthinobacterium lividum (strain BR01) that produced prodigiosin when grown at cool temperatures. Further studies of the diversity of J. lividum revealed that the Alaskan soil also harbors violacein-producing J. lividum purple strains (e.g. strain BP01), and that representatives of the purple and red strains exhibit high levels of resistance to beta-lactam antibiotics. J. lividum BR01 is the first example of a prodigiosin-producer in the betaproteobacteria, and the genes required for prodigiosin production in this strain differ from those of a well-studied prodigiosin producer, Serratia sp. The results show that extensive characterization of culture collections from novel environments remains fruitful in expanding the known space of microbial diversity and natural product production.