Microbiology, 2021

1200 E • Glossary
nucleus where ribosomal RNA
biosynthesis occurs and preribosomal
complexes are made
nucleoside analog chemical that is
structurally similar to a normal nucleotide
base that can be incorporated into DNA
instead of normal bases during replication
but that has different base pairing rules
than the normal base for which it was
substituted, inducing mutation
nucleotide excision repair (dark repair)
enzymatic mechanism to repair
pyrimidine dimers by cutting the dimercontaining
DNA strand on both sides of
dimer, removing the intervening strand
and replacing the bases with the correct
ones
nucleotide nucleic acid monomer
composed of a pentose sugar, a phosphate
group, and a nitrogenous base
nucleus a membrane-bound structure of
eukaryotic cells that houses the DNA
genome
numerical aperture a measure of a lens’s
ability to gather light
O
objective lenses on a light microscope,
the lenses closest to the specimen,
typically located at the ends of turrets
obligate aerobe organism that requires
oxygen for growth
obligate anaerobe organism that dies in
the presence of oxygen
obligate intracellular pathogen
microorganism that cannot synthesize its
own ATP and, therefore, must rely on a
host cell for energy; behaves like a parasite
when inside a host cell, but is
metabolically inactive outside of a host cell
observational study a type of scientific
study that involves measurement of study
subjects on variables hypothesized to be
associated with the outcome of interest,
but without any manipulation of the
subjects
ocular lens on a microscope, the lens
closest to the eye (also called an eyepiece)
oil immersion lens a special objective
lens on a microscope designed to be used
with immersion oil to improve resolution
Okazaki fragment short fragment of DNA
made during lagging strand synthesis
oligopeptide peptide having up to
approximately 20 amino acids
opacity the property of absorbing or
blocking light
operator DNA sequence located between
the promoter region and the first coding
gene to which a repressor protein can bind
operon a group of genes with related
functions often found clustered together
within the prokaryotic chromosome and
transcribed under the control of a single
promoter and operator repression
sequence
ophthalmia neonatorum inflammation of
the conjunctiva in newborns caused by
Neisseria gonorrhoeae transmitted during
childbirth
opisthotonos characteristic symptom of
tetanus that results in uncontrolled
muscular spasms and backward arching
of the neck and spine
opportunistic pathogen microorganism
that can cause disease in individuals with
compromised host defenses
opsonin any molecule that binds to and
coats the outside of a pathogen, identifying
it for destruction by phagocytes (examples
include antibodies and the complement
proteins C3b and C4b)
opsonization process of coating a
pathogen with a chemical substance (an
opsonin) that allows phagocytic cells to
recognize, engulf, and destroy the
pathogen more easily
optimum growth pH the pH at which an
organism grows best
optimum growth temperature the
temperature at which a microorganism’s
growth rate is highest
optimum oxygen concentration the ideal
concentration of oxygen for a particular
microorganism
oral herpes an infection caused by herpes
simplex virus that results in cold sores,
most commonly on and around the lips
oral thrush Candida infection of the
mouth
orchitis inflammation of one or both of the
testes
organic molecule composed primarily of
carbon; typically contains at least one
carbon atom bound to one or more
hydrogen atoms
organotroph chemotroph that uses
organic molecules as its electron source;
also known as chemoheterotroph
origin of replication specific nucleotide
sequence where replication begins
oropharynx area where air entering
mouth enters the pharynx
osmosis diffusion of water across a
semipermeable membrane
osmotic pressure the force or pressure
generated by water diffusing across a
semipermeable membrane, driven by
differences in solute concentration across
the membrane
osteomyelitis inflammation of bone tissue
otitis externa an infection of the external
ear canal, most commonly caused by
Pseudomonas aeruginosa; often called
swimmer’s ear
otitis inflammation of the ear
otitis media with effusion accumulation
of fluid inside the middle ear with or
without infection
Ouchterlony assay test in which antigen
and antisera are added to neighboring
wells in an agar gel, allowing visualization
of precipitin arcs
outer membrane a phospholipid bilayer
external to the peptidoglycan layer found
in gram-negative cell walls
oxazolidinones class of synthetic protein
synthesis inhibitors that interfere with
formation of the initiation complex for
translation and prevent translocation of
the growing protein from the ribosomal A
site to the P site
oxidation reaction chemical reaction that
removes electrons (often as part of H
atoms) from donor molecules, leaving
them oxidized
oxidative phosphorylation mechanism
for making ATP that uses the potential
energy stored within an electrochemical
gradient to add P i to ADP
oxygenic photosynthesis type of
photosynthesis found in plants, algae, and
cyanobacteria, and in which H 2 O is used
as the electron donor to replace an
electron lost by a reaction center pigment,
resulting in oxygen as a byproduct
P
P (peptidyl) site functional site of an
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