Talk:Cells Eukaryotes and Prokaryotes

From CellBiology

A field guide to bacterial swarming motility

Nat Rev Microbiol. 2010 Sep;8(9):634-44. doi: 10.1038/nrmicro2405. Epub 2010 Aug 9.

Kearns DB. Author information

Abstract How bacteria regulate, assemble and rotate flagella to swim in liquid media is reasonably well understood. Much less is known about how some bacteria use flagella to move over the tops of solid surfaces in a form of movement called swarming. The focus of bacteriology is changing from planktonic to surface environments, and so interest in swarming motility is on the rise. Here, I review the requirements that define swarming motility in diverse bacterial model systems, including an increase in the number of flagella per cell, the secretion of a surfactant to reduce surface tension and allow spreading, and movement in multicellular groups rather than as individuals. PMID 20694026

Two faces of the prokaryote concept

Int Microbiol. 2006 Sep;9(3):163-72.

Sapp J.

Department of Biology,York University, Toronto, Ontario, Canada. jsapp@yorku.ca

Abstract Bacteria had remained undefined when, in 1962, Roger Y. Stanier and C.B. van Niel published their famed paper The concept of a bacterium. The articulation of the prokaryote-eukaryote dichotomy was a vital moment in the history of biology. This article provides a brief overview of the context in which the prokaryote concept was successfully launched in the 1960s, and what it was meant to connote. Two concepts were initially distinguished within the prokaryote-eukaryote dichotomy at that time. One was organizational and referred to comparative cell structure; the other was phylogenetic and referred to a natural classification. Here, I examine how the two concepts became inseparable; how the prokaryotes came to signify a monophyletic group that preceded the eukaryotes, and how this view remained unquestioned for 15 years, until the birth of molecular evolutionary biology and coherent methods for bacteria phylogenetics based on 16S rRNA. Today, while microbial phylogeneticists generally agree that the prokaryote is a polyphyletic group, there is no agreement on whether the term should be maintained in an organizational sense.

"The prokaryote-eukaryote dichotomy was indeed universally accepted as a natural order of things until bacterial taxonomy based on evolutionary relationships was revitalized and reformed in the 1970s with the emergence of rRNA phylogenetics. Based on those data and congruent biochemical comparisons, a fundamental trilogy, three domains or superkingdoms of Archaea, Eubacteria, and Eucarya were proposed to replace the previous bifurcation of life forms. At the molecular and biochemical levels, the difference between Archaea and Eubacteria is held to be far greater than that between a human and a plant."

PMID: 17061206 http://www.ncbi.nlm.nih.gov/pubmed/15944457

http://mmbr.asm.org/cgi/content/full/69/2/292?view=long&pmid=15944457

Prokaryote Motility

Actin-based motility of intracellular microbial pathogens

Microbiol Mol Biol Rev. 2001 Dec;65(4):595-626, table of contents.

Goldberg MB.

Infectious Disease Division, Massachusetts General Hospital, Boston, Massachusetts 02114, USA. mgoldberg1@partners.org

Abstract A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells. These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells. Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface. The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells. Each of these organisms utilizes preexisting mammalian pathways of actin rearrangement to induce its own actin-based motility. Particularly remarkable is that while all of these microbes use the same or overlapping pathways, each intercepts the pathway at a different step. In addition, the microbial molecules involved are each distinctly different from the others. Taken together, these observations suggest that each of these microbes separately and convergently evolved a mechanism to utilize the cellular actin assembly machinery. The current understanding of the molecular mechanisms of microbial actin-based motility is the subject of this review.

PMID: 11729265 http://www.ncbi.nlm.nih.gov/pubmed/11729265

http://mmbr.asm.org/cgi/content/full/65/4/595?view=long&pmid=11729265