Nutrition induced pleomorphism and budding mode of reproduction in Deinococcus radiodurans

To strengthen the concept on pleomorphism in bacteria, we report here different cell morphologies of Deinococcus radiodurans in response to variation in nutrient concentration. From our studies we attempt primary evidence towards the presence of significant population of monomer cells of D. radiodurans in specific culture condition. In this report we also illustrate with scanning electron micrographs an unusual budding mode of reproduction in D. radiodurans which was not reported till date for this group of bacteria.In a holistic view the study reflects on bacterial shape (morphotypes) and the physiological adaptation to a particular nutrient environment. The discovery of budding mode of reproduction in Deinococcus will be of interest to microbiologists. It can serve as a model system to understand the mechanism of budding process at molecular level.The Deinococcaceae are a family of non-spore-forming bacteria which exhibit extreme resistance to ionizing radiation and desiccation [1-3]. D. radiodurans strain R1 (the strain used in the present study) is the well characterized member of Deinococcaceae and exist as individual tetrads in its natural milieu [4]. During different growth phases, D. radiodurans predominantly exists as tetrads, with a fraction of population as aggregates of sextet or octets [5]. Daly et al., [6] observed that D. radiodurans grows in tryptone, glucose and yeast extract (TGY) medium as clusters of two cells (diplococci) in early stages of growth and as four cells (tetracocci) in late growth phase. Venkateswaran et al., [2] demonstrated that D. radiodurans grows as diplococci in a defined minimal medium (DMM) which contains mixture of amino acids and other constituents. Chou & Tan [7] reported that the concentration of mono/divalent cations (Na, K, Li, Mg and Ca) plays a major role in multicell formation in Deinococcus and low salt medium such as TGY or nutrient broth also produce similar multicell forms in salt added media. In response to salt