## 3 SRB Impact on Environments and Humans
### Sewer System Negative Impacts of SRB Action  
Sewer systems are by nature nutrient-rich and are therefore home to a wide range of microorganisms, including SRB that grow either in sediment or biofilm at the bottom of the pipes. Problems are caused by their H\({}_{2}\)S production. It diffuses from the lower layers of the biofilm up to the oxic conditions, where it is oxidized biologically (for example by bacteria of the family _Thiomonas_ and _Thiobacillus_) or instead abiotically [60]. Abiotic oxidation of sulfide represents the oxidation where physico-chemical processes are included, meaning that the reduced iron and/or manganese oxidation leads to the improvement of the kinetics of sulfide oxidation with the formation of oxidized metals [60]  
The resulting sulfates (based on the SO\({}_{4}\)\({}^{2}\) - ion) and sulfuric acid (H\({}_{2}\)SO\({}_{4}\)) react with concrete, which is a material frequently used for the construction of sewers. One of the common components of concrete is gypsum (CaSO\({}_{4}\)), which comes into contact with sulfates corrodes to ettrintigite (Ca\({}_{6}\)Al\({}_{2}\)(SO\({}_{4}\))\({}_{3}\)(OH)\({}_{12}\)\(\cdot\)26H\({}_{2}\)O) [61]. Ettrintigite expands and causes cracks and loss of concrete coherence. Due to the production of sulfuric acid, pH also decreases, resulting in biofilms formed by acidophilic microorganisms, which further increases the surface acidity. H2S and acetate produced by SRB are lowering pH on the metal surface. This process could lead to a higher corrosion rate [62]. Additionally, sulfane threatens the health and life of sewer workers [63; 64]. Constantly, new strains of SRB are found, such as _Desulfo-vibrio vulgaris_ strain Hildenborough (isolated from sediment of a heavy metal impacted lake). Bacteriophages related to specific SRB are also usually revealed with new strains [65; 66]. Already in 1973, scientists from the University of Kansas observed phage-infecting _Desulfo-vulgaris_. Bacterial cells were stressed by both UV radiation and mitomycin C. At first glance, no lysis was observed after antibiotic addition, but the size of individual cells increased and appeared more pleomorphic. Therefore, the suspension was centrifuged several times, and then, the pellet was examined under an electron microscope. The observerswere not sure whether they were phage, but they mention that \"particle morphology is typical of phage belonging to Bradley Group A\" [67]. The differences among bacteriophages of different _Desulfovibrio vulgaris_ strains can be overviewed through the differences between _D. vulgaris_ NCIMB 8303 and _D. desulfuricans_ ATCC 13541. These strains showed different restriction enzyme cleavage patterns and different protein profiles [65; 66; 67]. [PERSON] and [PERSON] (1987) found phage capable of gene transduction in _Desulfovibrio desulfuricans_. It was observed that the virus is capable of transferring rifampicin and malidixic acid resistance between strains [68]. A lytic bacteriophage was isolated in 1988 in Japan. Scientists separated phage from muddy sediment samples collected at low tide and tested it on a laboratory strain of _Desulfovibrio salexigens_. Based on electron microscope observations, they reported that these viruses have a regular icosahedral head and a long non-contractile flagellum. They were morphologically similar to coliphage \(\lambda\), which is a member of the family _Styloviridae_. The nucleic acid has been characterized as dsDNA [69; 70]. In the early 1990s, further attempts were made in Kansas to induce lysogenic phages in _Desulfovibrio vulgaris_, which is a strain of Hildenborough and _Desulfovibrio desulfuricans_. This was successful, based on restriction analysis and DNA hybridization, and it was found that the viruses of the two organisms did not share DNA homology and thus probably did not share a common ancestor. Further research has focused on comparing strains of _D.