Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology

notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations

Effects of Thermoradiation Treatments on the DNA of Bacillus Subtilis Endospores

Endospores of the bacterium, Bacillus subfilis, have been shown to exhibit a synergistic rate of cell death when treated with particular levels of heat and ionizing radiation in combination. This synergism has been documented for a number of different organisms at various temperatures and radiation doses (Sivinski, H.D., D.M. Garst, M.C. Reynolds, C.A. Trauth, Jr., R.E. Trujillo, and W.J. Whitfield, ''The Synergistic Inactivation of Biological Systems by Thermoradiation,'' Industrial Sterilization, International Symposium, Amsterdam, 1972, Duke University Press, Durham, NC, pp. 305-335). However, the mechanism of the synergistic action is unknown. This study attempted to determine whether the mechanism of synergism was specifically connected to the DNA strand breakage--either single strand breakage or double strand breakage. Some work was also done to examine the effect of free radicals and ions created in the spore body by the radiation treatments, as well as to determine the functionality of repair enzymes following heat, radiation, and thermoradiation treatments. Bacillus subtilis spores were treated at combinations of 33 kr/hr, 15 kr/hr, 105 C, 85 C, 63 C, and 50 C. Some synergistic correlation was found with the number of double strand breaks, and a strong correlation was found with the number of single strand breaks. In cases displaying synergism of spore killing, single strand breakage while the DNA was in a denatured state is suspected as a likely mechanism. DNA was damaged more by irradiation in the naked state than when encased within the spore, indicating that the spore encasement provides an overall protective effect from radiation damage in spite of free radicals and ions which may be created from molecules other than the DNA molecule within the spore body. Repair enzymes were found to be functional following treatments by radiation only, heat only, and thermoradiation

Sugar transport in Sulfolobus solfataricus is mediated by two families of binding protein-dependent ABC transporters

The extreme thermoacidophilic archaeon Sulfolobus solfataricus grows optimally at 80°C and pH 3 and uses a variety of sugars as sole carbon and energy source. Glucose transport in this organism is mediated by a high-affinity binding protein-dependent ATP-binding cassette (ABC) transporter. Sugar-binding studies revealed the presence of four additional membrane-bound binding proteins for arabinose, cellobiose, maltose and trehalose. These glycosylated binding proteins are subunits of ABC transporters that fall into two distinct groups: (i) monosaccharide transporters that are homologous to the sugar transport family containing a single ATPase and a periplasmic-binding protein that is processed at an unusual site at its amino-terminus; (ii) di- and oligosaccharide transporters, which are homologous to the family of oligo/dipeptide transporters that contain two different ATPases, and a binding protein that is synthesized with a typical bacterial signal sequence. The latter family has not been implicated in sugar transport before. These data indicate that binding protein-dependent transport is the predominant mechanism of transport for sugars in S. solfataricus.