Microbiology, 2021

E • Glossary 1197
infection caused by Neisseria meningitidis
that results in an inflammation of the
meninges
meningoencephalitis inflammatory
response that involves both the brain and
the membranes that surround it
MERS Middle East respiratory syndrome;
first described in Saudi Arabia in 2013;
caused by a zoonotic coronavirus that
results in flu-like symptoms
mesophile a microorganism that grows
best at moderate temperatures, typically
between about 20 °C and 45 °C
metabolism all of the chemical reactions
inside of cells
metachromatic granule a type of
inclusion containing volutin, a
polymerized inorganic phosphate that
appears red when stained with methylene
blue
metagenomics the sequencing of genomic
fragments from microbial communities,
allowing researchers to study genes from a
collection of multiple species
metatranscriptomics the science of
studying a collection of mRNA molecules
produced from microbial communities;
involves studying gene expression
patterns from a collection of multiple
species
methanogen microorganism that
produces gaseous methane
methicillin-resistant Staphylococcus
aureus (MRSA) pathogen resistant to all β-
lactams through acquisition of a new lowaffinity
penicillin-binding protein, and
often resistant to many other drug classes
metronidazole antibacterial and
antiprotozoan drug of the nitroimidazole
class that is activated in anaerobic target
cell and introduces DNA strand breakage,
thus interfering with DNA replication in
target cells
MHC I molecule glycoprotein expressed
on the surface of all nucleated cells and
involved in the presentation of normal
“self” antigens and foreign antigens from
intracellular pathogens
MHC II molecule glycoprotein expressed
only on the surface of antigen-presenting
cells and involved in the presentation of
foreign antigens from pathogens ingested
by phagocytosis
micelle simple spherical arrangement of
amphipathic lipid molecules with
nonpolar tails aggregated within the
interior and polar heads forming the outer
surface
microaerophile organism that requires
oxygen at levels lower than atmospheric
concentration
microarray analysis a technique used to
compare two samples of genomic DNA or
cDNA; the DNA or cDNA fragments are
immobilized on a chip and labeled with
different fluorescent dyes, allowing for
comparison of sequences or geneexpression
patterns
microbe generally, an organism that is too
small to be seen without a microscope;
also known as a microorganism
microbial death curve graphical
representation of the progress of a
particular microbial control protocol
microbial ecology study of the
interactions between microbial
populations microbiology the study of
microorganisms
microbiome all prokaryotic and
eukaryotic microorganisms and their
genetic material that are associated with a
certain organism
microfilament cytoskeletal fiber
composed of actin filaments
microinjection the direct injection of DNA
into the cytoplasm of a eukaryotic cell
using a glass micropipette
micronucleus smaller nucleus in ciliate
protists that have two nuclei; diploid,
somatic, and used for sexual reproduction
through conjugation
micronutrient indispensable element
present in cells in lower amounts than
macronutrients; also called trace element
microorganism generally, an organism
that is too small to be seen without a
microscope; also known as a microbe
microsporidia fungi that lack
mitochondria, centrioles, and
peroxisomes; some can be human
pathogens
microtiter plates plastic dishes with
multiple small wells
microtubule hollow tube composed of
tubulin dimers (α and β tubulin); the
structural component of the cytoskeleton,
centrioles, flagella, and cilia
miliary tuberculosis hematogenous
dissemination and spread of
Mycobacterium tuberculosis from
tubercles
minimal bactericidal concentration
(MBC) lowest antibacterial drug
concentration that kills ≥99.9% of a
starting inoculum of bacteria
minimal inhibitory concentration (MIC)
lowest concentration of an antibacterial
drug that inhibits visible growth of a
bacterial strain
minimum growth pH lowest pH value that
an organism can tolerate for growth
minimum growth temperature lowest
temperature at which a microorganism
will divide or survive
minimum permissible oxygen
concentration lowest concentration of
oxygen at which an organism will grow
missense mutation point mutation that
results in a different amino acid being
incorporated into the resulting
polypeptide
mitochondrial matrix the innermost
space of the mitochondrion enclosed by
two membranes; the location of many
metabolic enzymes as well as the
mitochondrial DNA and 70S ribosomes
mitochondrion (plural: mitochondria)
large, complex organelle that is the site of
cellular respiration in eukaryotic cells
mitosis(also, karyokinesis) period of the
cell cycle during which the duplicated
chromosomes are separated into identical
nuclei; includes prophase, prometaphase,
metaphase, anaphase, and telophase
mitotic phaseperiod of the cell cycle
during which duplicated chromosomes
are distributed into two nuclei and
cytoplasmic contents are divided; includes
karyokinesis (mitosis) and cytokinesis
mode of action way in which a drug
affects a microbe at the cellular level
moist-heat sterilization protocol that
involves steam under pressure in an
autoclave, allowing the steam to reach
temperatures higher than the boiling point
of water
mold a multicellular fungus, typically
made up of long filaments
molecular cloning the purposeful