Bacterial biomass and cell size distributions in lakes: more and larger cells in anoxic waters

We measured bacterial abundance, cell size distribution, and related microbiological and geochemical parameters in 20 stratified lakes from three regions in the U.S. Both largest cell size and greatest bacterial abundance occurred in anoxic waters. Bacterial size distributions from the hypolimnia of lakes that were oxic were identical to those in surface waters. Bacteria from anoxic hypolimnia were 2–10 times larger than those from oxic water and cell size was independent of temperature under either oxic or anoxic conditions. For all lakes and strata, bacterial abundance was strongly related to the concentration of total phosphorus (TP). Cell size was not related to TP or to bacterial abundance, suggesting that abundance and size may be regulated by different processes. Bacterial biomass (calculated from the product of mean cell size and bacterial abundance) was typically 4 times greater in anoxic than in oxic waters of lakes.This study was supported by the National Science Foundation (BSR 89- 17962 and BSR 90- 19873) and is a contribution to the Institute of Ecosystem Studies

Amino Acid Analysis

Amino acid analysis is used to determine the amino acid content of amino acid–, peptide- and protein-containing samples. With minor exceptions, proteins are long linear polymers of amino acids connected to each other via peptide bonds. The first step of amino acid analysis involves hydrolyzing these peptide bonds. The liberated amino acids are then separated, detected, and quantified. The method was first developed by Moore, Stein and coworkers in the 1950s using HCl acid hydrolysis, and, despite considerable effort by many workers, the basic methodology remains relatively unchanged. This unit provides an overview and strategic planning for amino acid analysis, discussing a range of methodologies and issues. In addition, several common methods used for analysis of l-amino acids are described in detail, including: HCl acid hydrolysis, performic acid oxidation for methionine and cysteine analysis, base hydrolysis for tryptophan analysis, analysis of free amino acids, and analysis of reactive lysine