General Microbiology

Abstract

Generally microbes can be divided into two categories: the cellular microbes (or organisms) and the acellular microbes (or agents). In the cellular camp we have the bacteria, the archaea, the fungi, and the protists (a bit of a grab bag composed of algae, protozoa, slime molds, and water molds). Cellular microbes can be either unicellular, where one cell is the entire organism, or multicellular, where hundreds, thousands or even billions of cells can make up the entire organism. In the acellular camp we have the viruses and other infectious agents, such as prions and viroids. In this textbook the focus will be on the bacteria and archaea (traditionally known as the “prokaryotes,”) and the viruses The scale of the “invisible world’; There are a thousand millimetres in a metre. There are a thousand microns (micrometres) in a millimetre, an E. coli bacterium is about a micron long – so a million of them lined up form a line a metre long, a cell of bakers yeast (a fungus) is about 10-15 microns in diameter. Some microscopic pond life is invisible to the naked eye, some are “just” visible. Viruses are very tiny, only a fraction of a micron (say 20 - 100 nanometres - billionths of a metre). Bacteria, fungi, and protozoa can be seen in a light microscope, but except for the larger protozoans, not with much internal detail. Viruses cannot be seen using a light microscope. Viruses can easily be seen using a transmission electron microscope, extensive details of cells can be analysed with an electron microscope. The “Branches” of microbiology; Bacteriologists - study bacteria, there are medical, agricultural, biotechnological Specializations. Mycologists - study fungi, there are medical, agricultural, biotechnological Specializations. Protozoologists, study small “animal - like” single celled organisms such as amoeba, and various disease causing parasites. Phycologists study algae. The study of lichens can also be regarded as a sub discipline of microbiology Parasitologists- a term generally used to describe those who study small animals as agents of disease (like some microscopic worms for instance) but also used to describe those who study protozoan pathogens. Immunology is often taught and researched in microbiology faculties