Secretion of amino acids by bacteria: Physiology and mechanism

Abstract

Although representing a common property of microorganisms and being widely used for biotechnological purposes, solute secretion has been relatively poorly studied in terms of biochemistry. In this review, various examples of metabotite secretion processes by bacteria are discussed with the emphasis on the mechanisms of amino acid secretion by coryneform bacteria. Among the metabolic concepts which may be applied to explain the physiological meaning of metabolite secretion, mainly two concepts are dealt with, i.e. the so-called 'overflow metabolism' on the one hand and the situation where non-metabolizable intermediates are accumulated and finally secreted on the other. In the central part of this review, the different concepts are discussed which have been put forward to mechanistically explain amino acid secretion under particular metabolic conditions and in particular strains of bacteria, i.e. secretion mediated (i) by diffusion, (ii) by the participation of amino acid uptake systems, and (iii) by the use of specific secretion systems. These concepts are then applied to amino acid secretion in Coo'nebacterium ghaamicum, and exemplified by detailed studies on the mechanism and regulation of the secretion of lysine, isoleucine and glutamate by C.glutamicum.

Bacterial Metabolism in Dental Biofilms

“…Although some sugars may be available from glycoproteins of the tissue fluid, the subgingival biofilm may be dependent on amino acids as nitrogen and energy sources. With a combination of extracellular proteases and peptidases, amino acid and peptide transport systems, and intracellular peptidases, the 78 CARLSSON ADV DENT RES APRIL 1997 bacteria will recover amino acids from their environment (Pritchard and Coolbear, 1993;Kramer, 1994;Steiner et aL, 1995). Many bacteria of the subgingival biofilms have proteolytic activity; among the most potent ones are Porphyromonas gingivalis and Treponema denticola (Potempa et aL, 1995;Rosen et aL, 1995).…”

Urea uptake and urease activity in Corynebacterium glutamicum

“…For amino acid production, a sufficient nitrogen supply is essential; this emphasizes the importance of detailed information on urea uptake and metabolism. Since we are interested in the physiology of C. glutamicum (Krämer 1994(Krämer , 1996, we investigated the mechanism of urea transport and utilization in this bacterium.…”

Mapping and identification of Corynebacterium glutamicum proteins by two‐dimensional gel electrophoresis and microsequencing

“…Since we are interested in regulatory processes related to amino acid production and transport [6,18,191 we applied 2-D PAGE on preparations of both cytoplasm and membranes in order to establish corresponding 2-D protein maps as a basis for comparative studies.…”