micrograzers

Micrograzers are small heterotrophic organisms that feed on microorganisms, primarily bacteria and tiny algae. They span a range of sizes from a few micrometers to a fraction of a millimeter and are dominated by protists such as ciliates, heterotrophic flagellates, and amoebae. In some contexts, micrograzers may also include very small metazoans, but the term is most often used to describe microbial-sized consumers.

Feeding and physiology rely on phagocytosis or similar ingestive mechanisms. Micrograzers capture and engulf bacterial or algal prey using structures like cilia, flagella, or pseudopods, then digest the prey intracellularly. Most are aerobic and rely on organic carbon derived from their prey. Some species are mixotrophic, gaining photosynthetic products in addition to ingesting prey, but grazing remains the primary mode of nutrition for many.

Ecological role and significance arise from their position in the microbial food web. Micrograzers regulate bacterial and algal populations, influence nutrient cycling by mineralizing organic matter, and help channel carbon through the microbial loop toward higher trophic levels. They also contribute to the turnover of dissolved organic matter and can alter microbial community composition through selective grazing.

Habitats and distribution are broad. Micrograzers occur in freshwater and marine systems, soils, leaf litter, biofilms, and wastewater treatment environments. They respond quickly to changes in nutrient availability, temperature, and moisture, and their abundance often tracks microbial community dynamics.

Importance and applications include use as model organisms in microbial ecology studies, indicators of ecosystem health, and potential agents in biotechnological processes such as biocontrol of bacteria in wastewater or engineered biofilms. Further research continues to clarify their roles across diverse environments.