Journal of Methods Microbiological Journal of Microbiological Methods 33 (1998) 203–210 Use of species distribution data in the determination of bacterial viability by extinction culture of aquatic bacteria a, b ,c * Pham X. Quang , Don K. Button a Department of Mathematical Sciences, University of Alaska Fairbanks, Fairbanks, AK, USA b Institute of Marine Science, University of Alaska Fairbanks, Fairbanks, AK, USA c Department of Chemistry and Biochemistry, University of Alaska Fairbanks, Fairbanks, AK, USA Received 29 December 1997; received in revised form 20 April 1998; accepted 20 April 1998 Abstract We show that bacterial viability can be calculated from the number of species arising in cultures comprised of seawater diluted to near extinction of the propagating organisms. Natural conditions are simulated by partitioning the culture against illuminated raw seawater to maintain a source of nutrients and a sink for waste products, and predators are eliminated by dilution to a statistical absence. Mean values for viability can be corrected for contaminants that may enter the culture by computing their probable entrance frequency as well. Viability determinations were found to be mildly sensitive to the number of species estimated to be present in the original sample. This novel procedure provides a significant improvement in the cultivation success of typical marine bacteria, and the formulations presented here lay the foundation for the quantitative analysis of the population structure.  1998 Elsevier Science B.V. All rights reserved. Keywords: Extinction culture; Flow cytometry; Marine bacteria; Speciation; Statistical theory; Viability 1. Introduction and alkalinities (Madigan and Marrs, 1997), they are called oligobacteria because of their ability to grow Chemoheterotrophic bacteria comprise about half at small concentrations of nutrients (Button et al., the biomass in aquatic systems (Button et al., 1996) 1993). Nutrition is complex because most expired with high total amounts due in part to propagation biomass from primary productivity is in the form of throughout the water column. A major result of their macromolecules too large for direct accumulation by activity is oxidation of organic chemicals produced bacterial transport systems, so extracellular enzymes by photosynthetic organisms and subsequent conver- must be proffered (Jones and Lock, 1989) to reduce sion to mineral nutrients, with concomitant contribu- these complex compounds to molecules of transport- tion to food webs through bacterivores (Andersen able size. Molecule capture is by permeases having a and Fenchel, 1985). Existing under a range of degree of specificity for the compounds (Nikaido and temperatures (Forterre et al., 1996), pressures (Kato Saier, 1992) and many permease types are therefore et al., 1996), salinities (Madigan and Marrs, 1997), required. The captured molecules are then metabo- lized through specific pathways comprised of several * enzymes, so the utilization of the organic compounds Corresponding author. Tel.: 11 907 4746550; e-mail: ffpxq@aurora.alaska.edu in the environment requires the synthesis of many 0167-7012 / 98 / $ – see front matter  1998 Elsevier Science B.V. All rights reserved. PII: S0167-7012(98)00045-1