Unit 1.1 Introduction to Microbiology
Outline
Learning Objectives
After reading the following, you should be able to:
- Be able to define the terms microbiology, microorganism and pathogen.
- Be able to give examples of the non-pathogenic roles that microorganism play.
- Be able to name the different types of microorganisms discussed in this course.
From boiling thermal hot springs to deep beneath the Antarctic ice, microorganisms can be found almost everywhere on earth in great quantities. Microorganisms or microbes, as they are also called) are small organisms. Most are so small that they cannot be seen without a microscope and the study of these organisms is known as Microbiology.
Most microorganisms are harmless to humans and, in fact, many are helpful. They play fundamental roles in ecosystems everywhere on earth, forming the backbone of many food webs. People use them to make biofuels, medicines, and even foods. Without microbes, there would be no bread, cheese, or beer. Our bodies are filled with microbes, and our skin alone is home to trillions of them.
Although much more is known today about microbial life than ever before, the vast majority of this invisible world remains unexplored. Microbiologists continue to identify new ways that microbes benefit and threaten humans. In this course we will be discussing several different categories of microorganism. These can be separated in to two broad categories: Prokaryotic microorganisms and Eukaryotic microorganisms, which will be discussed in greater detail in Unit 2.
Prokaryotic Microorganisms
Bacteria are single celled microbes that are found in nearly every habitat on earth, including within and on humans. Bacteria are prokaryotic because their genetic material (DNA) is not housed within a true nucleus. Most bacteria are harmless or helpful, but some are pathogens, causing disease in humans and other animals.
Most bacteria have cell walls that contain peptidoglycan. They have a wide range of metabolisms and can grow in a variety of environments, using different combinations of nutrients. Some bacteria are photosynthetic, producing oxygen. Other types of bacteria are non-photosynthetic, obtaining their energy from organic or inorganic compounds in their environment. Environmentally, they play a major role in decomposition, nitrogen fixation and are the foundation of many food webs. In our bodies, non-pathogenic bacteria are involved in a number of processes, such as the production of vitamin K and making feces brown.
Archaea are also unicellular prokaryotic organisms. Archaea and bacteria have different evolutionary histories, as well as significant differences in genetics, metabolic pathways, and the composition of their cell walls and membranes. Unlike most bacteria, archaeal cell walls do not contain peptidoglycan, but their cell walls are often composed of a similar substance called pseudopeptidoglycan. Like bacteria, archaea are found in nearly every habitat on earth, even extreme env