Microbiology terms - S
- scale up
- Conversion of an industrial process from a small laboratory setup to a large
commercial fermentation.
- scarlet fever
- Characteristic reddish skin rash resulting from an exotoxin produced by cells
of Streptococcus pyogenes.
- secondary antibody response
- Antibody made upon second (subsequent) exposure to antigen; mostly of
the class IgG.
- secondary metabolite
- A product excreted by a microorganism near the end of the growth phase or
during stationary phase.
- secondary structure
- The initial pattern of folding of a polypeptide or a polynucleotide, usually the
result of hydrogen bonding.
- secretion vector
- A DNA vector in which the protein product is both expressed and secreted
(excreted) from the cell.
- selection
- Placing organisms under conditions where the growth of those with a
particular genotype will be favored.
- selective medium
- A medium which allows the growth of certain types of microorganisms in
preference to others. For example, an antibiotic-containing medium allows
the growth of only those microorganisms which are resistant to this
antibiotic.
- semiconservative replication
- DNA synthesis yielding new double helices, each consisting of one parental
and one progeny strand.
- septicemia
- Infection of the bloodstream by microorganisms.
- septum (plural septa)
- A crosswall (partition) dividing a parent cell into two daughter cells during
binary fission or occuring between adjacent cells in the hyphae.
- serology
- The study of antigen-antibody reactions in vitro.
- serum
- Fluid portion of blood remaining after the blood cells and materials
responsible for clotting are removed.
- sexually transmitted disease (STD)
- A disease whose usual means of transmission is by sexual contact.
- sheath
- 1. A secreted, tubular structure formed around a chain of cells or around a
bundle of filaments; cells within a sheath may or may not subsequently
separate from the sheath.
2. A layer of outer membrane covering the bacterial flagella.
- Shine-Dalgarno sequence
- A short stretch of nucleotides on a prokaryotic mRNA molecule upstream
of the translational start site, that serves to bind to ribosomal RNA and
thereby bring the ribosome to the initiation condon on the mRNA.
- shuttle vector
- A DNA vector which can replicate in two different organisms, used for
moving DNA between unrelated organisms.
- sickle-cell anemia
- A genetic trait which confers resistance to malaria but which causes a
reduction in numbers of red blood cells.
- signal sequence (signal peptide)
- A short stretch of amino acids found at the beginning of proteins that are
typically rich in hydrophobic amino acids which helps transport the entire
polypeptide through the membrane.
- signature sequence
- Short oligonucleotides of unique sequence found in 16S ribosomal RNA of
a particular group of prokaryotes.
- single-cell protein
- Protein derived from microbial cells for use as food or a food supplement.
- site-directed mutagenesis
- The insertion of a different nucleotide at a specific site in a DNA molecule
using synthetic DNA methodology.
- 16S rRNA
- A large polynucleotide (about 1500 bases) which functions as a part of the
small subunit of the ribosome of prokaryotes and from whose sequence
evolutionary information can be obtained; the eukaryotic counterpart is 18S
rRNA.
- slime layer
- A diffused layer of polysaccharide exterior to the bacterial cell wall.
Compare with capsule and glycocalyx.
- slime mold
- A nonphototrophic eukaryotic microorganism lacking cell walls, which
aggregate to form fruiting structures (cellular slime molds) or simply masses
of protoplasm (acellular slime molds).
- Southern blot
- Hybridization of a single strand of nucleic acid (DNA or RNA) to DNA
fragments immobilized on a filter. Compare with northern and Western blot.
- species
- In microbiology, a collection of closely related strains sufficiently different
from all other strains to be recognized as a distinct unit.
- specific epithet
- The label (or designation) of a particular species in the binomial
nomenclature system. For example, "coli" is the specific epithet of
Escherichia coli.
- specificity
- The ability of the immune response to interact with individual antigens.
- spheroplast
- A spherical, osmotically sensitive cell derived from a bacterium (or any cell
with cell wall) by loss of some but not all of the rigid wall layer. If all the rigid
wall layer has been completely lost, the structure is called protoplast.
- spirillum (plural: spirilli)
- 1. A bacterium with a spiral shape which is relatively rigid (i.e. not flexible,
compare with spirochaete.
2. The bacterium in the genus Spirillum.
- spirochaete (spirochete)
- A gram-negative bacterium characterized by the flexibly spiral shape and the
possession of axial filaments.
- spontaneous generation
- The hypothesis that living organisms can originate from nonliving matter.
- spore
- A general term for resistant resting strutures formed by many prokaryotes
and fungi.
- sporozoa
- Nonmotile parasitic protozoa.
- stalk
- An elongate structure, either cellular or excreted, which anchors a cell to a
surface.
- stationary phase
- The period during the growth cycle of a population in which growth ceases.
- stem cell
- Fetal cells that give rise to bone marrow, blood cells, and B and T cells.
- stereoisomer
- A mirror image form of a molecule. Both have the same molecular and
structural formula but different in their stereo arrangement of molecular
positions.
- sterile
- Free of living organisms and viruses.
- sterilization
- Treatment resulting in death of all living organisms and viruses in a material.
- steroid
- Any tetracyclic hydrocarbons which is derived from
perhydrocyclopentanophenanthrenea. Important examples of steroids are
cholesterol, and sterol; several hormones are also steroids such as sex
hormones and corticosteroid hormones. Even vitamin D is based on the
steroid structure.
- sterol
- Any steroid-based alcohol having a hydrocarbon (aliphatic) side-chain of
8-10 carbons at the 17-beta position and a hydroxyl group (-OH) at the
3-beta position (that's why it's an alcohol). Cholesterol is one type of sterols.
Because of its hydrophilic property at the -OH end and hydrophobic at the
hydrocarbon side chain, it can be incorporated into the lipid bilayers of the
cytoplasmic membrane. However, sterols only exist in the cytoplasmic
membranes of eukaryotes while in prokaryotes, virtually all do not have
sterol in their membranes except mycoplasmas, a group of cell wall-less
bacteria.
- stop codon
- A codon which signals the termination of translation
- streptobacilli
- Rods that remain attached in chains after cell division.
- streptococci
- Cocci that remain attached in chains after cell division.
- strain
- A population of cells all descended from a single cell; also a clone.
- stromatolites
- Laminated microbial mats, typically built from layers of filamentous and other
microorganisms which can become fossilized.
- substrate
- The molecule undergoing reaction with an enzyme.
- substrate-level phosphorylation
- Synthesis of high-energy phosphate bonds through reaction of inorganic
phosphate with an activated (usually) organic substrate.
- sulfatara
- A hot, sulfur-rich, generally acidic environment, commonly inhabited by
hyperthermophilic Archaea.
- supercoil
- Highly twisted form of circular DNA.
- superoxide anion
- A harmful derivative of oxygen capable of oxidative destruction of cell
components.
- suppressor
- A mutation that restores wild-type phenotype without altering the original
mutation, usually arising by mutation in another gene.
- symbiosis
- The living together of two different organisms.
- syntrophy
- A nutritional situation in which two or more organisms combine their
metabolic capabilities to catabolize a substance not capable of being
catabolized by either one alone.
- systemic
- Not localized in a particular place of the body; an infection disseminated
widely through the body is said to be systemic.
- sulfate-reudcing bacterium
- A prokaryote which is able to reduce sulfate SO42- (as a terminal electron
acceptor) using electrons donated from organic acids, fatty acids, alcohols
or hydrogen (electron donors).
- syphilis
- A chronic human disease caused by Treponema pallidum. Infection
generally occurs by direct contact with lesions of syphilis.
Compiled by Tsute Chen, Converted by Ben Hoyt