L-forms and the unusual formation of progeny in cell wall-less bacteria: recognizing the old roots of new science

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COMMENTARY

L-forms and the unusual formation of progeny in cell wall-less bacteria: recognizing the old roots of new science Hans Herbert Martin

Received: 23 November 2009 / Accepted: 26 December 2009 / Published online: 8 January 2010 © Springer-Verlag 2010

In a recent impressive leading article in MICROBE (Gest 2009), Howard Gest, at Indiana University, recalled the value of “Rediscovering Pioneering Research in Microbial Ecology” for present-day science. With such advice in mind, this commentary attempts to compare current and historic research in an important and very active Weld of molecular microbiology, the complex mechanism of cell division in bacteria, with a special view on contributions by studies of cell wall-less bacteria. According to a current model (Goehring and Beckwith 2005), the typical binary Wssion of the bacterial cell is achieved by a membrane-bound “division machine” (divisosome), where the major cytoskeletal protein FtsZ, combined with 10 or more essential proteins (Z-ring), cooperates with the division mechanism of the cell wall with its speciWc shape-conferring exoskeleton peptidoglycan. Very timely, in EVERYBODY’S DARWIN, the “Darwin 200 Special Issue” of NATURE, and with suggestive relevance for bacterial evolution, JeV Errington and colleagues at Newcastle University described. “Life without a wall or division machine in Bacillus subtilis” (Leaver et al. 2009). By genetic operations eliminating FtsZ function and shutting down the synthesis of peptidoglycan the authors converted rod-shaped cells of B. subtilis into the L-form, a mutant population of fragile, presumably cell wall-less, but still viable protoplasts. These L-form protoplasts prolifer-

Communicated by Erko Stackebrandt. H. H. Martin (&) Technical University Darmstadt, FB 10-Biologie, Darmstadt, Germany e-mail: [email protected]

ated in a very unusual way by extruding multiple small protoplasts, assumed to be progeny, from their surfaces. The authors conclude that this budding type of proliferation may be a primeval mechanism of reproduction conserved from early progenitors of bacteria, prior to the evolution of the cell wall and division machine. The novelty of this research and its signiWcance for molecular studies on evolution were highlighted in an editorial comment and interview in NATURE (This Nature Issue 2009; Abstractions Nature 2009) and in other news media. In a Corrigendum (Leaver et al. 2009) it was then pointed out that, already in the mid-nineteen-Wfties, Gertraud and Otto Kandler at the University of Munich, Germany (Kandler and Kandler 1954; Kandler et al. 1954), had reported the propagation by a budding mechanism instead of binary Wssion in two unrelated groups of cell wall-less bacteria, in the Pleuropneumonia-like Organisms, belonging to the naturally wall-less Mycoplasmas, and in L-forms of diVerent Gram-negative bacteria. The authors followed the growth of microcultures by continued phase contrast microscopy and time lapse photography. Formation of progeny from repeated pseudopodal outgrow