Although environmental and sanitary engineers are aware of the importance of microbial activity, many civil and architectural engineers do not appreciate the part microbiological processes play in, for example, biodeterioration of concrete and other construction materials. Microbes promote also weathering of rock to soils and swelling of soils, clogging of boreholes and irrigation systems, and biofouling in embankment dams. Microbes promote the biodeterioration by their enzymes. The paper involves the biodeterioration of concrete structures. In order to help understanding of its process, a complex dynamic ecosystems model on biodeterioration of concrete structures is presented. In order to understand the alteration by biodeterioration, total carbon (TC) and total nitrogen (TN) of test piece of fresh concrete and of various deteriorated concrete structures were measured with C-N analyzer. Observations of microbial activity on the surfaces of deteriorated concrete structures were also conducted by using digital microscope. Finally, the Importance of biology, especially, of microbiology and ecology in civil engineering is emphasized.