Glossary

Adhesins: surface appendages that facilitate adhesion or adherence of bacterial cells to other cells or to surfaces

Aminoacids: monomeric units of proteins mostly consisting of carbon, hydrogen, oxygen and nitrogen atoms

Antibiotic: a chemical that inhibits the growth of microorganisms or kills them

Antimicrobial resistance: the acquired ability of a microorganism to grow in the presence of an antimicrobial drug to which the microorganism is originally sensitive

Archaea: phylogenetically related prokaryotes distinct from Bacteria

Bacteraemia: bacterial shedding into the bloodstream in large numbers after bacteria grow extensively in tissues

Bacillus (pl. bacilli): A bacterium with a cylindrical, rod shape

Bacteria: all prokaryotes that are not members of the domain Archaea

Bacteriophage: a virus that infects prokaryotic cells

Biofilm: communities of bacterial cells attached to a surface and encased in adhesive polysaccharides excreted by the cells

Carbohydrate: organic sugars, containing carbon, hydrogen and oxygen atoms, the most abundant one being the glucose

Capsid: the protein coat of a virus

Capsule: a polymer coat consisting of a dense, well-defined polysaccharide or protein layer closely surrounding a cell

Cell: the fundamental unit of living matter

Cell membrane: the permeability barrier of the cell, separating the cytoplasm from the environment; consists of lipid and protein

Cell wall: a structural layer outside the cell membrane giving the cell its rigidity and acting as a filtering mechanism

Chloroplast: the chlorophyll-containing organelle of photosynthetic eukaryotes

Chromosome: compact, organized state of DNA carrying genes essential to cell function

Coccus (pl. cocci): A spherical-shaped bacterium

Commensalism: a relationship between different species organisms of which one benefits from the relationship without harming the other

Cytoplasm: the fluid portion of a cell, bounded by the cell membrane but excluding the nucleus (if present)

Cytoplasmic membrane: thin structure that completely surrounds the cell

DNA: stands for deoxyribonucleic acid, the hereditary genetic information of cells and some viruses essential to produce progeny

Domain: the highest level of biological classification

Ecology: the study of organisms in their natural environments

Ecosystem: organisms plus their non-living environment

Endospore: a highly heat-resistant, thick-walled, differentiated cell produced by certain gram-positive Bacteria

Enrichment culture: a method for isolating microorganisms from nature using specific culture media and incubation conditions

Endotoxin: cell-bound or intracellular toxic molecules that are released in large amounts only when cells are lysed

Enterotoxin: an exotoxin that acts on the small intestine, generally causing massive secretion of fluid into the intestinal lumen, leading to vomiting and diarrhea

Enzymes: protein catalysts that speed up chemical reactions

Epidemic: a disease occurring in an unusually high number of individuals in a population at the same time

Exotoxin: proteins released extracellularly as the organism grows and which may cause damage in regions far removed from the site of microbial growth

Eukaryote: a cell having a membrane-bound nucleus and usually other organelles

Evolution: change in a line of descent

Fever: an abnormal increase in body temperature

Fimbriae: short, filamentous protein structures on the surface of bacterial cells, involved in attachment

Flagellum: a long, thin cellular appendage capable of rotation and responsible for swimming and swarming movements in prokaryotic cells

Fungi: eukaryotic microorganisms that contain rigid cell walls

Gene: segment of DNA that encodes a full protein or regulatory RNA molecules essential for cell function

Genome: whole set of genes of a cell or a virus

Glycosidic bond: a type of bond that links sugar units

Gram-negative: a prokaryotic cell whose cell wall contains relatively little peptidoglycan but contains an outer membrane composed of lipopolysaccharide, lipoprotein, and other complex macromolecules

Gram-positive: a prokaryotic cell whose cell wall consists chiefly of peptidoglycan and lacks the outer membrane of gram-negative cells

Habitat: the location in an environment where a microbial population resides

Homeostasis: the biological process by which conditions (temperature, blood sugar level etc.) are controlled to maintain levels that are beneficial for the body

Immunity: the ability of an organism to resist infection

Immunocompromised (immunodeficient): having dysfunctional or completely nonfunctional immune system

Inflammation: a nonspecific reaction to harmful agents such as toxins and pathogens

Lipid: glycerol bonded to fatty acids or other molecules such as phosphate

Lipopolysaccharide: building block of the additional layer of cell wall in Gram-negative bacteria called the outer membrane, not constructed solely of phospholipid as the cytoplasmic membrane but of polysaccharide and protein

Lysozyme: a naturally occurring enzyme found in bodily secretions of humans such as tears, saliva, and mothers’ milk

Metabolism: all biochemical reactions in a cell

Macromolecule: the collective name given to the four chemical components making up the cell: proteins, nucleic acids, lipids and polysaccharides

Microorganism: a microscopic organism consisting of a single cell or cell cluster, including the viruses

Microscope: a magnifying instrument used to look at objects that are too tiny to be seen by the naked eye

Mitochondrion: the respiratory organelle of eukaryotic organisms

Molds: filamentous fungi

Monomer: a building block of a polymer

Monotrichous: flagellum located at one end of the cell (trichous means ‘hair’

Morphology: cell shape

Motility: the property of movement of a cell under its own power

Multidrug resistance: the acquired resistance of a microorganism to many antimicrobial drugs

Mutation: a permanent and inheritable alteration of the nucleotide sequence of the genome

Nucleic acid: polymers of nucleotides found in a cell

Nucleoid: the aggregate form that bacterial chromosome is stored as

Nucleotide: a nitrogen base(adenine, guanine, cytosine, thymine, or uracil), a molecule of phosphate, and a sugar, either ribose (in RNA) or deoxyribose (in DNA) grouped together

Nucleus: a membrane-enclosed structure that contains the chromosome in eukaryotic cells

Organelle: a unit membrane-enclosed structure present in the cytoplasm of eukaryotic cells

Opportunistic pathogen: an infectious microorganism that is normally harmless or commensal but takes advantage of an opportunity not normally available, such as a host with a weakened immune system

Outbreak: the occurrence of a large number of cases of a disease in a short period of time

Pandemic: a worldwide epidemic

Pathogen: a disease-causing microorganism

Periplasm: a gel-like region between the outer surface of the cytoplasmic membrane and the inner surface of the lipopolysaccharide layer of gram-negative Bacteria

Peritrichous: flagella located in many places around the surface of the cell (peri means ‘around’, trichous means ‘hair’)

Peptide: aminoacids grouped together

Peptidoglycan: a thin sheet composed of two sugar derivatives and a small group of aminoacids, primarily responsible for the strength of the cell wall

Phenotype: all the observable characteristics of an individual

Phospholipid: lipids containing a phosphate group and having a structural role in the cytoplasmic membrane

Photosynthesis: the series of reactions in which energy is produced by light-driven reactions and carbondioxide is fixed into cell material

Phylogeny: the evolutionary relationships between organisms

Physiology: pertinent with the normal functioning of an organism

Pili: protein structure found in few numbers on the cell surface of bacteria and involved in attachment and exchange of genetic material

Plague: an endemic disease in rodents caused by the bacterium Yersinia pestis that is occasionally transferred to humans through the bite of a flea

Plasma membrane: the same as cell membrane

Plasmid: an extrachromosomal genetic element nonessential for growth, usually arranged in a circular fashion

Polymer: a chemical compound formed from repeating units called monomers by polymerization

Polypeptide: molecule of many aminoacids linked via peptide bonds

Polysaccharide: a long chain of carbohydrates connected by glycosidic bonds, primarily present in the cell wall

Porin: protein present in the outer membrane Gram-negative bacteria, forming small membrane holes

Prokaryote: a cell lacking a membrane-enclosed nucleus and other organelles

Protein: a group of peptides that form a molecule of specific biological function

Proteome: all the proteins present in a cell, tissue or organism at any one time

Protozoa: unicellular eukaryotic microorganisms that lack cell walls

Pure culture: a culture containing a single kind of microorganism

Quorum sensing: bacterial cell-cell communication mechanism

Ribosome: a cytoplasmic particle that is part of the protein-synthesizing machinery of the cell

RNA: stands for ribonucleic acid, the building blocks of proteins in the form of messenger RNA, transfer RNA, and ribosomal RNA

Slime molds: eukaryotic microorganisms that lack cell walls and that aggregate to form fruiting structures

Spirilla: rod-shaped bacteria twisted into spirals

Spirochetes: tightly coiled bacteria

Spontaneous generation: the hypothesis that living organisms can originate from non-living matter

Sterile: absence of all living organisms and viruses

Swarming motility: coordinated, multicellular translocation of bacteria on semi-solid surfaces

Toxin: a microbial protein endowed with the capacity of inducing host specific disease-associated physiological effects

Virulence: the relative ability of a pathogen to cause disease

Virus: a major class of microorganisms with packaged RNA or DNA that are not cells and can only reproduce inside living cells

Yeasts: unicellular fungi