Typically, a microbiologist.
Microbiology is a subdiscipline of Biology (but may also be considered by some to be a subdiscipline of micrology), and there are also subdisciplines of microbiology (e.g. virology, bacteriology).
Pathologist
very very small . for example MICROScopic organisms are so small that they may only be viewed under a magnifying glass.
A specialist of a particular subject
Plankton is a mass of floating organisms in water comprising of microscopic algae and protozoa. Plankton is the primary food source of many animals. In origin it is a Greek word meaning wandering or drifting. In modern usage it was coined by the German physiologist Viktor Hensen (1835 - 1924_
The disivion of organisms into groups, or classes, based on specific characteristics​
the organisms rely on each other for survival.
Virologist
Micro- meaning microscopic. Too small to be seen with the naked eye. Short for Microscopic. There are micro organisms in this forest environment.
Gerontologists are specialists in the study of diseases of the elderly.
Pathogenics.
A neurologist is a specialist in the study of the nervous system, including the brain and spinal cord.
Decomposers are the creatures that break down dead organisms and are often microscopic like bacteria.
An Imunologist works on preventing communicable diseases. A Nutritionist works on preventing dietary deficiency diseases. An Internist is a physician who works on preventing the beginning of or the negative effects of preventable diseases and chronic diseases.
Epidemiology is the study of factors affecting the health and illness of populations. The specialist is called an epidemiologist.
An animal, usually. A consumer is an organism that must eat other organisms to obtain its enrgy. Microscopic organisms can also be consumers. Plants and some microscopic organisms are producers, meaning they create their food from sunlight through photosynthesis.
One who devotes himself to some specialty; as, a medical specialist, one who devotes himself to diseases of particular parts of the body, as the eye, the ear, the nerves, etc.
Epidemologist
A pediatrician.A pediatricianPediatricians are medical doctors that specialize in dealing with children.