Water contaminated with various pathogens houses a host of parasitic and microbial infections. Sialidases may act as pathogenic factors in microbial infections. A lichen is a symbiosis of a macroscopic fungus with photosynthetic microbial algae or cyanobacteria. Handshakes are known to spread a number of microbial pathogens. The risk is microbial and viral contamination. Intestinal ILCs are exposed to dietary, microbial, and endogenous metabolites. It inhibits nucleic acid synthesis by disrupting the DNA of microbial cells. Upon detection of microbial antigens, the host systemic immune system is activated. They also influence the quantity of plant and microbial biomass present. Mars may have niche subsurface environments where microbial life might exist. BSA is also used as a nutrient in cell and microbial culture. Erlenmeyer flasks are also used in microbiology for the preparation of microbial cultures. There are two types of biopesticides - biochemical and microbial. Other species are important in commercial microbial fermentations. Environmental urease activity is often measured as an indicator of the health of microbial communities.