Fungus is a Bacteria
Bacteria and fungi occur in all environments. In humans, these lifeforms can be harmless passengers, participate in beneficial biological processes, or cause disease. Bacterial and fungal infections affect people of all ages and range from minor to potentially life-threatening. Bacteria and fungi have similarities and differences that influence their disease-causing potential and treatment.
Cells are the simplest units of life, and are categorized into two main groups. Bacteria are prokaryotes, one-celled organisms that lack a structure called a nucleus, a membrane-encased collection of genetic material. Although bacteria are unicellular, they often collect in chains or clusters.
Fungi are eukaryotes. Fungal cells include a well-defined nucleus as well as other distinct structures with varied functions. Fungi occur in unicellular and multicellular forms, including mushrooms, lichens, algae, yeast and mold. Most medically relevant fungi exist as unicellular yeasts and molds. Fungi are generally larger than bacteria and utilize more complex biologic processes.
With rare exception, disease-causing bacteria possess a rigid cell wall surrounding their cell membrane. Most also have a capsule or slime layer that encases the cell wall. Fungi also have cell walls. However, the composition of bacterial and fungal cell walls differ. Bacterial cell walls consist primarily of peptidoglycan, a compound made of a backbone of sugar molecules with attached short chains of amino acids. Fungal cell walls contain primarily polysaccharides, such as chitin, beta-glucan and mannan. Polysaccharides are large chemicals consisting of interconnected sugar molecules. Amino acids and proteins are not major constituents of fungal cell walls.
The cell walls of bacteria and fungi protect them from the environment and give them shape, among other functions. However, the chemical and structural differences between their cell walls is one reason antibiotic medicines that are effective against bacteria are ineffective against fungi, and vice versa.
As unicellular organisms, bacterial cells do not grow per se. However, they can multiply very rapidly. Disease-causing bacteria multiply by an asexual process called binary fission, in which the parent bacterium divides in two. Most pathogenic bacteria, meaning those that cause disease, can double in number within 15 to 60 minutes. This explains why serious bacterial infections, such as meningococcal meningitis or a bloodstream infection, usually progress very quickly.