1.1 Flashcards
Microorganisms and the human body (5)
bacteria viruses fungi protozoa helminths (worms)
microbiome (4)
bacteria
viruses
fungi
protozoa
Parasitic organisms
Symbionts that harm or live at the expense of their host
Commensal organisms
Normal microbiota - microbes frequently found on or within
the bodies of healthy persons
Infection
–growth and multiplication of parasite on or within host
Infectious disease
–disease resulting from infection
Pathogen
–any parasitic organism that causes infectious disease
primary (frank) pathogen –
causes disease by direct
interaction with host
opportunistic pathogen –
causes disease only under certain
circumstances
Pathogenicity
–ability of parasite to cause disease
Virulence factor
- any component of a pathogenic microbe that is required for
or that potentiates its ability to cause disease
steps in infectious disease (6)
encounter entry spread multiplication damage outcome
Encounter (3)
Exogenous
Endogenous
Congenital
- Entry (2)
ingress
penetration
Ingress:
inhalation, ingestion
Penetration:
microbes pass through epithelia directly (via
attachment and internalization), insect bites, cuts
and wounds, organ transplants and blood
transfusions
Spread (3)
lateral propagation versus dissemination
anatomical factors
active participation by microbes
Multiplication (2)
environmental factors (e.g. temperature) subversion of host defenses
Mucormycosis (fungal infection) in
rhinocerebral form, almost always with (2)
hyperglycemia and metabolic acidosis
Damage (2)
direct damage
immune response
Outcome (3)
microbe wins, host wins, or they learn to coexist
Normal microbiota-
microbes frequently found on or within
the bodies of healthy persons
commensal organisms
Colonization by bacteria occurs rapidly after
birth
— of bacterial species are part of the normal flora.
Thousands
The Human Microbiome
the collection of all the microorganisms living
in association with the human body
eukaryotes, archaea, bacteria and viruses
Bacteria in an average human body number — times more than human cells
ten
contain a total of about 1000 more genes than are present in the human genome because of their small size bacteria make up only about 1-3% of our body mass
2 to 6 pounds of bacteria in a 200-pound adult
Bacteria in the microbiome of a healthy individual are essential for maintaining —
health
Bacteria in the microbiome of a healthy individual are essential for maintaining health (6)
produce some vitamins that we do not have the genes to make
break down our food to extract nutrients we need to survive
teach our immune systems how to recognize dangerous invaders
produce helpful anti-inflammatory compounds that fight off other disease-causing microbes
occupy space to crowd out disease-causing microbes
detoxification of carcinogens but sometimes are the source of carcinogen production
Changes in the composition of our microbiomes correlate with
numerous disease states
source of infection
manipulation of these communities could be used to treat disease
Locations in body with largest amounts of bacteria (5)
skin (especially moist areas) respiratory tract (nose and oropharynx) digestive tract (mouth and large intestine) urinary tract (anterior parts of urethra) genital system (vagina)
Other body locations have small numbers of bacteria.
Remainder of respiratory and digestive tracts
Some body locations are sterile. (4)
blood, cerebrospinal fluid, synovial fluid, deep tissues
Transient vs. resident organisms
Pathogenicity/virulence also depend on the
host
Definition of pathogen not so certain
periodontitis -
overgrowth of particular bacteria in gingival
crevices
pneumonia -
defenses lowered and microaspirations of
pneumococci
catheter-associated infections -
staphylococci
Oral flora includes (4)
bacteria (and archeae)
fungi
protozoa (eukaryotes)
viruses
~— different species of bacteria are estimated to
be present in the oral cavity
700
Oral habitats (5)
buccal mucosa dorsum of tongue tooth surfaces crevicular epithelium dental appliances
Issues for microbial cells (3)
Nutritional fluxes
Maintaining occupancy
Resistance to damage
anatomical features that create areas that are
difficult to clean (4)
- shape and topography of teeth
e. g. fissures - malalignment of teeth
- poor quality of restorations (e.g. fillings and bridges)
- non-keratinized sulcular epithelium
saliva fxns (7)
mixture of inorganic ions
organic constituents
salivary pellicle
source of food
promotes aggregation of bacteria, facilitating their clearance from mouth
inhibits growth of microbes by non-specific defense factors
maintains pH
saliva organic constituents (2)
proteins
glycoproteins (e.g. mucin)
salivary pellicle
promotes adhesion of bacteria on tooth surfaces
organic components form a coating on tooth surfaces
gingival crevicular fluid (5)
flushing microbes out of crevice source of nutrients for microbes maintains pH specific and non-specific defense factors phagocytosis
phagocytosis
— main phagocyte
neutrophils
microbial factors (4)
competition for adhesion receptors
toxin production
metabolic end products
coaggregation
metabolic end products
negative vs. positive effects
local pH
will vary with diet as a result of
bacterial metabolism
redox potential
a measure of oxygen levels in locality
Factors modulating oral microbial growth (9)
anatomical features that create areas that are difficult to clean saliva GCF microbial factors local pH redox potential antimicrobial therapy diet iatrogenic factors
iatrogenic factors
dental scaling
— are an absolute requirement for
all living organisms
membranes
plasma membrane encompasses the —
cytoplasm
some prokaryotes also have
internal
membrane systems
most DO NOT
The Plasma Membrane contains (2)
lipids and proteins
– lipids usually form a bilayer
– proteins are embedded in or associated with lipids
PM characteristics (4)
highly organized, asymmetric, flexible, and
dynamic
The asymmetry of most membrane lipids polar ends (2) nonpolar ends (2)
• polar ends – interact with water – hydrophilic • nonpolar ends – insoluble in water – hydrophobic
peripheral proteins
– loosely associated with the membrane and
easily removed
integral proteins
– embedded within the membrane and not easily
removed
Functions of the plasma
membrane (4)
• separation of cell from its environment
• selectively permeable barrier
• location of crucial metabolic processes
• detection of and response to chemicals in
surroundings with the aid of special
receptor molecules in the membrane
selectively permeable barrier (2)
– some molecules are allowed to pass into or out
of the cell
– transport systems aid in movement of
molecules
Inclusion Bodies
• granules of organic or inorganic material
that are stockpiled by the cell for future use
Inclusion Bodies
some are enclosed by a
single-layered
membrane
– membranes vary in composition
– some made of proteins; others contain lipids
Ribosomes
• complex structures consisting of protein and
RNA
Ribosomes site of
protein synthesis
Ribosomes
p vs e
prokaryotic are smaller than eukaryotic ribosomes
– prokaryotic ribosomes =
70S
– eukaryotic ribosomes =
80S
S =
Svedburg unit
The Nucleoid (3)
• irregularly shaped region
• location of chromosome
– usually 1/cell
• not membrane bound
In actively growing cells, the nucleoid has projections; these probably contain
DNA
being actively
transcribed
The prokaryotic chromosome (3)
• a closed circular, double-stranded DNA
molecule
• looped and coiled extensively
• nucleoid proteins probably aid in folding
– nucleoid proteins differ from —
histones
some prokaryotes have > - chromosome
1
some prokaryotes have chromosomes
composed of
linear double-stranded DNA
a few genera have — nucleoids
membrane-delimited
Plasmids (4)
• usually small, closed circular DNA molecules • exist and replicate independently of chromosome • not required for growth and reproduction • may carry genes that confer selective advantage (e.g., drug resistance)
The Prokaryotic Cell Wall
• rigid structure that lies
just outside the plasma
membrane
Functions of cell wall (4)
- provides characteristic shape to cell
- protects the cell from osmotic lysis
- may also contribute to pathogenicity
- may also protect cell from toxic substances
Bacteria are divided into two major groups
based on the response to Gram-stain
procedure
– gram-positive bacteria stain purple
– gram-negative bacteria stain pink
• staining reaction due to
cell wall structure
Periplasmic space
• gap between plasma membrane and cell
wall (gram-positive bacteria) or between
plasma membrane and outer membrane
(gram-negative bacteria)
periplasm
– substance that occupies periplasmic space
Periplasmic enzymes
• found in
periplasm of gram-negative
bacteria
Periplasmic enzymes fxn (4)
– nutrient acquisition
– electron transport
– peptidoglycan synthesis
– modification of toxic compounds
Exoenzymes (2)
• secreted by gram-positive bacteria
• perform many of the same functions that
periplasmic enzymes do for gram-negative
bacteria
Peptidoglycan Structure (3)
• important component of both gram-positive
and gram-negative bacteria
• polysaccharide formed from peptidoglycan
subunits
• two alternating sugars form backbone
two alternating sugars form backbone (2)
– N-acetylglucosamine
– N-acetylmuramic acid
Gram-Positive Cell Walls (2)
• composed primarily of peptidoglycan • also contain large amounts of teichoic acids
teichoic acids
• polymers of glycerol
or ribitol joined by
phosphate groups
Gram-Negative Cell Walls (3)
• consist of a thin layer of peptidoglycan
surrounded by an outer membrane
• outer membrane composed of lipids,
lipoproteins, and lipopolysaccharide (LPS)
• no teichoic acids
Braun’s lipoproteins connect outer
membrane to —
peptidoglycan
Adhesion sites (2)
– sites of direct contact (possibly true membrane
fusions) between plasma membrane and outer
membrane
– substances may move directly into cell through
adhesion sites
Lipopolysaccharides (LPSs)
• consist of three parts
– lipid A
– core polysaccharide
– O side chain (O antigen)
Importance of LPS (4)
• protection from host defenses (O antigen)
• contributes to negative charge on cell
surface (core polysaccharide)
• helps stabilize outer membrane structure
(lipid A)
• can act as an endotoxin (lipid A)
Other characteristics of outer
membrane
• more permeable than plasma membrane due
to presence of
porin proteins and transporter
proteins
porin proteins form channels through which
small molecules (600-700 daltons) can pass
Capsules, Slime Layers, and SLayers
• layers of material lying — the cell wall
outside
capsules (2)
- usually composed of polysaccharides
* well organized and not easily removed from cell
slime layers (1)
• similar to capsules except diffuse, unorganized and
easily removed
glycocalyx (2)
– network of polysaccharides extending from the
surface of the cell
– a capsule or slime layer composed of
polysaccharides can also be referred to as a
glycocalyx
More functions of outer membrane (4)
• protection from viral infection or predation
by bacteria
• protection from chemicals in environment
(e.g., detergents)
• motility of gliding bacteria
• protection against osmotic stress
fimbriae (2)
– short, thin, hairlike, proteinaceous appendages
• up to 1,000/cell
– mediate attachment to surfaces
sex pili (2)
– similar to fimbriae except longer, thicker, and less numerous (1-10/cell) – required for mating
• monotrichous –
one flagellum
• polar flagellum –
flagellum at end of cell
amphitrichous –
one flagellum at each end
of cell
lophotrichous –
cluster of flagella at one or
both ends
peritrichous –
spread over entire surface of
cell
Flagellar Ultrastructure
• 3 parts
– filament
– basal body
– hook
The Bacterial Endospore (3)
• formed by some bacteria
• dormant
• resistant to numerous environmental
conditions
resistant to numerous environmental
conditions (4)
– heat
– radiation
– chemicals
– desiccation
An Overview of Eukaryotic Cell Structure (4)
• membrane-delimited nuclei • membrane-bound organelles that perform specific functions • more structurally complex than prokaryotic cell • generally larger than prokaryotic cell
The Endoplasmic Reticulum
irregular network of branching and fusing membranous tubules and flattened sacs (cisternae – s., cisterna)
rough (granular) ER (2)
– ribosomes attached
– synthesis of secreted proteins by ER-associated ribosomes
smooth (agranular) ER (2)
– devoid of ribosomes
– synthesis of lipids by ER-associated enzymes
Functions of ER (3)
– transports proteins, lipids, and other materials within cell
– major site of cell membrane synthesis
– synthesis of lysosomes
The Golgi Apparatus
• membranous organelle
made of cisternae
stacked on each other
dictyosomes
– stacks of cisternae
The Golgi Apparatus
• involved in (3)
modification,
packaging, and
secretion of materials
lysosomes (2)
– membrane-bound vesicles
– contain hydrolytic enzymes needed for
digestion of macromolecules
endocytosis
– uptake of solutes or particles by enclosing them
in vesicles or vacuoles pinched off from the
plasma membrane
• Phagocytosis –
particles or bacterial cells
• Pinocytosis -
solutes
Mitochondria (2)
• site of tricarboxylic acid cycle activity • site where ATP is generated by electron transport and oxidative phosphorylation
Mitochondrial structure (3)
- outer membrane
- inner membrane
- matrix
inner membrane (2)
– highly folded to form cristae (s., crista)
– location of enzymes and electron carriers for electron transport and
oxidative phosphorylation
matrix (2)
– contains ribosomes, mitochondrial DNA, and large calcium
phosphate granules
– contains enzymes of the tricarboxylic acid cycle and the β- oxidation pathway for fatty acids
nucleus
– membrane-bound structure that
houses genetic material of cell
chromatin (3)
– dense fibrous material within nucleus
– contains DNA
– condenses to form chromosomes
during cell division
nuclear envelope (2)
– double membrane structure that
delimits nucleus
– penetrated by nuclear pores
pores allow materials to be
transported into or out of nucleus
The molecular unity of
prokaryotes and eukaryotes (3)
- same basic chemical composition
- same genetic code
- same basic metabolic processes
