Kawaguchi Tomohiro, Decho Alan W
Department of Environmental Health Sciences, School of Public Health, University of South Carolina, Columbia 29208, USA.
Prep Biochem Biotechnol. 2002 Feb;32(1):51-63. doi: 10.1081/PB-120013161.
Bahamian soft marine stromatolites consist of cyanobacterial biofilms and carbonate sand grains (ooids) embedded in their extracellular polymeric secretions (EPS). EPS were isolated from natural marine stromatolites and the laboratory cultured stromatolite forming cyanobacterium isolate Schizothix sp. Laboratory investigations were conducted to examine biochemical characteristics and the role of EPS in the inhibition of CaCO3 precipitation. EPS consisted of acid polysaccharides and proteins. SDS-PAGE and amino acid analysis suggested that EPS from both soft marine stromatolite and Schizothrix sp. mat contained small proteins (38 kD and 45 kD) enriched in aspartic acid and glutamic acid. Also, immuno blotting suggested that natural EPS contain high molecular weight acid polysaccharide (500 k) which may represent cross-linked products of laboratory cultured Schizothrix sp. acid polysaccharide (300 k). EPS from both soft marine stromatolite and laboratory cultured Schizothrix sp. inhibited CaCO3 precipitation in vitro, as determined using pH drift assays examining pH decrease which occur in response to CaCO3 precipitation. PH drift assays of enzymatically and chemically modified EPS isolated from soft marine stromatolite and laboratory cultured Schizothrix sp. indicated that both uronic acids and protein fractions may be involved in the inhibition of CaCO3 precipitation.
巴哈马软质海洋叠层石由蓝藻生物膜和嵌入其细胞外聚合物分泌物（EPS）中的碳酸盐沙粒（鲕粒）组成。从天然海洋叠层石和实验室培养的形成叠层石的蓝藻分离株裂须藻属（Schizothix sp.）中分离出EPS。进行了实验室研究，以检查生化特性以及EPS在抑制碳酸钙沉淀中的作用。EPS由酸性多糖和蛋白质组成。SDS-PAGE和氨基酸分析表明，来自软质海洋叠层石和裂须藻属菌垫的EPS均含有富含天冬氨酸和谷氨酸的小蛋白质（38 kD和45 kD）。此外，免疫印迹表明天然EPS含有高分子量酸性多糖（500 k），这可能代表实验室培养的裂须藻属酸性多糖（300 k）的交联产物。使用pH漂移测定法测定pH值下降来确定，来自软质海洋叠层石和实验室培养的裂须藻属的EPS在体外均抑制碳酸钙沉淀，pH值下降是由碳酸钙沉淀引起的。对从软质海洋叠层石和实验室培养的裂须藻属中分离出的经酶促和化学修饰的EPS进行的pH漂移测定表明，糖醛酸和蛋白质部分可能都参与了对碳酸钙沉淀的抑制作用。
