Chapter 8 - 3

03 Biology

Measuring Microbial Activity

Microbes, or tiny organisms, make up the majority of the Earth’s living biomass. They are invisible to the naked eye.

Therefore, biologists must use specific methods to study and measure the activity of these organisms.

Although their minute size makes them somewhat difficult to observe, scientists have developed two tools for studying microbial activity.

These are radioisotopes and microelectrodes.

A radioisotope is an atom with an unstable nucleus.

It releases its excess energy as radiation. The radiation chemically alters the microorganism.

When used to study microbes, this radiation allows microbiologists to assess the chemicals released.

A) Radioisotopes can be used to study microbial activitynin a variety-of environments.

B) They are often used in the field of medicine for certain tests and treatments.

For example, doctors can inject a radioisotope into a patient suspected to have cancer.

The patient then undergoes a PET scan.

C) The radioisotope highlights the tumors on the scan.

This aids doctors in determining the exact cause of a medical condition.

Subsequently, they can treat the illness. Radioisotopes can also be used to eliminate harmful bacteria in foods.

D) Some types of meat contain parasites or pathogenic bacteria. Radioactive isotopes can target the specific bacteria and irradiate them. This kills the bacteria without harming the rest of the meat.

A microelectrode is an electrical device that can deliver an electric current to a non−metallic surface. Microelectrodes can be used to detect metabolic, or energy−producing, processes in microbes. A) In one study, biologists tried to determine why one type of bacteria was able to multiply so quickly in a certain environment.

B) They used microelectrodes to measure the levels of carbon dioxide and oxygen at different depths in a minute environment. They discovered that oxygen was depleted in the first fifty micrometers. As the oxygen decreased, the carbon dioxide increased. The toxic bacteria were allowed to thrive.

C) The highly specific nature of the microelectrodes provided scientists with the exact answers they needed.

D) The radioactive nature of radioisotopes and the ability of microelectrodes to work within tiny environments render both of these methods useful to biologists in various ways.

A) For example, microbial diseases such as the West Nile virus (WNV) and cholera negatively affect the world’s mortality and morbidity rates.

B) In 2005, 2,949 cases of WNV were reported in the United States. There were 116 deaths from the virus.

C) In addition, many of the negative changes made in the Earth’s environment begin at the microbial level. Since microbes are some of nature’s tiniest organisms, they provide valuable information about making positive changes in the environment that start at the most fundamental level.

D) Through the study of microbial activity, biologists have discovered more about the production and consumption of gases that affect the atmosphere. They have also learned about the transformation of these greenhouse gases and other toxic elements. Scientists use this information to develop strategies that may -help reverse negative climatic trends.