Methodology forEstimating NumbersofFree-Living andAttached Bacteria inEstuarine Water

摘要: Afundamental problem inestuarine microbiology studies istheaccurate determination ofthedensity inthe watercolumnofbothfree-living bacteria andthose attached tosuspended particulate matter. When a water sample isfiltered andthefilter isviewed byepifluorescence microscopy, counts canbemadeofthenumbersof whichare seen on thefilter background (free-living) andthosewhichappeartolieon sediment particles (both free-living andattached). Withonly theadditional knowledge oftheproportion ofthefilter area covered byparticles (aquantity thatisstraightforwardly determined bystereological point counting), results fromgeometric probability were usedtodetermine theexpected numberofbacteria whicharehiddenby andhence toprovide anestimation schemeforthetruedensities offree-living andattached bacteria. Variance equations based Taylor series aregiven, anda partial checkofthemethodisattempted with controlled mixtures ofbacteria andsediment. Analternative procedure isalsoproposed, inwhichthenatural attached/free-living ratio isaltered byan intervention experiment, allowing an estimation whichisless model dependent butmore labor intensive. Bothmethods areapplied toaseries ofsamples fromtheTamarestuary, United Kingdom, takeninApril 1985.A notable conclusion isthatthere arealways more than inthewatercolumnthroughout theestuary.