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

Production and properties of 2,3-butanediol: III. Studies on the biochemistry of carbohydrate fermentation by Aerobacillus polymyxa

Carbon balances have been obtained for the fermentation of glucose, xylose, pyruvic acid, and mannitol by Aerobacillus polymyxa. The chief products from glucose are 2,3-butanediol, ethanol, carbon dioxide, and hydrogen; in addition small amounts of acetic acid and acetoin are formed. In glucose fermentations under the conditions used the butanediol: ethanol ratio is about 1:1. The products of xylose fermentation are very similar, although the butanediol: ethanol ratio is shifted in favour of ethanol. From pyruvic acid the chief end-products are acetoin, acetic acid, carbon dioxide and hydrogen with almost no butanediol and ethanol production. In the fermentation of mannitol a large amount of lactic acid is produced, while butanediol production is markedly decreased, the butanediol: ethanol ratio being 1:7.Peer reviewed: YesNRC publication: Ye

Production and properties of 2,3-butanediol II. Strains of Aerobacillus polymyxa in relation to filterability and butanediol production

Under laboratory conditions it has been found that most strains of Aerobacillus polymyxa split off variants that differ substantially in: colony formation; appearance of wheat mashes after fermentation; filterability of these mashes; and their ability to produce 2,3-butanediol and ethanol. It has been impossible to demonstrate a close correlation between particular colony types and their usefulness for commercial 2,3-butanediol production. By selection it has been possible to obtain strains that are excellent both from the standpoint of mash filterability and product yield. Preservation of cultures in lyophile tubes prevents further variation during storage.Peer reviewed: YesNRC publication: Ye

Production and properties of 2,3-butanediol: I. Fermentation of wheat mashes by Aerobacillus polymyxa

Isolation of Aerobacillus strains with desirable fermentative characteristics was facilitated by pasteurization of the original inoculum. Both cultural characteristics and fermentative capacity of the original isolates were extremely variable. Dissociation into more variant types occurred in later generations giving rise to further differences in fermentative characteristics.In the preparation of mashes particle size of wheat is unimportant in relation to yield provided the kernel has been broken. Since prolonged cooking is harmful, a standard procedure of sterilization for 1\u2002hr. at 121 \ub0C. has been adopted. Mashes containing over 15% wheat by weight are inefficiently fermented. Acid production in the mash may be controlled by the addition of excess calcium carbonate at the beginning of the fermentation, or by the addition of ammonia as required. The most satisfactory fermentation temperature is about 32.5 \ub0C.The addition of yeast extract, malt extract, dried yeast, or corn steep liquor is essential for the preparation of an active inoculum. Fermentation of whole wheat mashes may also be enhanced by yeast extract. Removal of the gluten has little effect, but the bran, shorts, germ, and soluble nitrogenous constituents are necessary for a normal fermentation. Pure wheat starch with inorganic supplements can be only partially utilized.Under anaerobic conditions fermentation of a 15% mash is complete in 60\u2002hr., but continuous removal of the carbon dioxide reduces this time to 48\u2002hr. The diol\u2013ethanol ratio for anaerobic fermentations is of the order of 1.3: 1.0. Aerobic conditions inhibit the fermentation, particularly ethanol formation, and 120\u2002hr. are required for completion. The diol\u2013ethanol ratio, however, may be raised to 3: 1 or higher.Peer reviewed: YesNRC publication: Ye

Mixotrophic metabolism by natural communities of unicellular cyanobacteria in the western tropical South Pacific Ocean

International audienceCyanobacteria are major contributors to ocean biogeochemical cycling. However, mixotrophic metabolism and the relative importance of inorganic and organic carbon assimilation within the most abundant cyanobacteria are still poorly understood. We explore the ability of Prochlorococcus and Synechococcus to assimilate organic molecules with variable C:N:P composition and its modulation by light availability and photosynthetic impairment. We used a combination of radiolabeled molecules incubations with flow cytometry cell sorting to separate picoplankton groups from the western tropical south Pacific Ocean. Prochlorococcus and Synechococcus assimilated glucose, leucine, and ATP at all stations, but cell-specific assimilation rates of N and P containing molecules were significantly higher than glucose. Incubations in the dark or with an inhibitor of photosystem II resulted in reduced assimilation rates. Light-enhanced cell-specific glucose uptake was generally higher for cyanobacteria (~50%) than for the low nucleic acid fraction of bacterioplankton (LNA, ~35%). Our results confirm previous findings, based mainly on cultures and genomic potentials, showing that Prochlorococcus and Synechococcus have a flexible mixotrophic metabolism, but demonstrate that natural populations remain primarily photoautotrophs. Our findings indicate that mixotrophy by marine cyanobacteria is more likely to be an adaptation to low inorganic nutrient availability rather than a facultative pathway for carbon acquisition