Microbes, such as bacteria and fungi, occur in just about every ecosystem and can associate with various types of organisms. In humans, they can be harmless passengers, even participating in biological processes. However, they can also cause tissue damage and tamper with your body functions to the point of causing disease. Both types of microbes have similarities and differences worth noting.
Cells are divided into two main groups, based on whether they have a nucleus or not. Eukaryotes have a well-defined nucleus, while prokaryotes do not. Classified as prokaryotes, bacteria include two major groups: eubacteria, which are medically relevant bacteria, and archaeabacteria, the oldest living organisms. When people mention bacteria, they are usually referring to eubacteria, or any of their numerous subgroups. Fungi, on the other hand, are parasitic eukaryotes. Most fungi occur as the unicellular yeasts or the filamentous molds. Bacteria are generally smaller in size but more numerous than fungi.
Except for mycoplasma, all bacteria feature a rigid cell wall surrounding their cell membrane. Fungi also have a cell wall. However, the main component of the bacterial cell wall is peptidoglycan, while chitin is predominant in fungal cell walls. Thus, antibiotics, which inhibit the formation of peptidoglycan, do not affect fungi. The cell wall determines the shape of the bacterium, which is usually rod-like, spheroid or corkscrew-like. Fungi and bacteria also differ in the specific details of their cell membrane compositions. Bacteria can also differ from each other, as some may have additional surface layers, flagella or pili.
Growth and Nutrition
Bacteria multiply via binary fission, a process whereby each parent bacterium divides into two daughter cells of similar sizes. Filamentous fungi, on the other hand, grow by branching and elongation, while yeasts reproduce by budding. Regarding their nutrition, fungi are saprophytes, that is, they feed on dead matter. That is why you usually find fungi in soil or water containing organic waste. They are referred to as heterotrophs, meaning they cannot synthesize their own food. In contrast, bacteria can be heterotrophic or autotrophic. Autotrophic bacteria produce their own food from light or chemical energy.
Bacteria and fungi also spread and can survive in extreme conditions via a process called sporulation. Sporulation involves repackaging genetic contents into small reproductive bodies called spores, which contain little water, have a low metabolism, do not divide and feature an impermeable, multilayered envelope. Fungal and bacterial spores look different, but are all highly resistant to heat, UV light and many cleaning agents. They can grow into new fungi and bacteria once the environment becomes nutritious again.
According to scientist Pamela Champe and colleagues, bacteria and fungi pathogens are microbes that can harm your body by producing toxic compounds or by direct infection. Many of the most famous pathogens are spore-formers, including the bacteria that cause anthrax, tetanus, botulism, gas gangrene and gastroenteritis. Common fungal infections include candidiasis, ringworm, athlete's foot and jock itch.
Fungi and bacteria are as indispensable as other microbes, because they release or make nutrients available from non-living sources and provide energy to ecosystems. Bacteria also help your body degrade intestinal contents and make certain vitamins. Additional beneficial uses include the fermentation of chemicals, such as alcohol; production of foods, such as wine, dairies, pickles and bread; production of recombinant hormones; waste decomposition; and antibiotic production.
- "Microbiology" (2nd Edition); Richard Harvey, Ph.D., Pamela Champe, Ph.D. and Bruce Fisher, M.D.; 2007