microorganisms and the human body Flashcards
Microorganisms and the human body
bacteria, viruses, fungi, protozoa= microbiome
bacteria is vast majority
helminths (worms)
Parasitic organisms
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/types
–any parasitic organism that causes infectious disease
–primary (frank) pathogen – causes disease by direct interaction with host
–opportunistic pathogen – causes disease only under certain circumstance
Pathogenicity
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 an infectious disease
encounter entry spread multiplication damage outcome
ways encounter of infectious diseases
Exogenous, Endogenous, or Congenital
ways of pathogen entry
Ingress: inhalation, ingestion
Penetration: microbes pass through epithelia directly (via
attachment and internalization), insect bites, cuts
and wounds, organ transplants and blood
transfusions
spread of infection
lateral propagation (localized) versus dissemination (systemic infection)
anatomical factors
active participation by microbes with motility
Multiplication of pathogen
environmental factors (e.g. temperature) can stimulate division subversion of host defenses
damage from infection
direct damage from pathogen or from immune response
infection outcomes
microbe wins, host wins, or they learn to coexist
Normal Microbiota
when does it form?
microbes frequently found on or within the bodies of healthy persons\ =commensal organisms
Colonization by bacteria occurs rapidly after birth.
Thousands of bacterial species are part of the normal flora
The Human Microbiome
the collection of all the microorganisms living in association with the human body
eukaryotes, archaea, bacteria and viruses
bacteria vs human cell anbundance
Bacteria in an average human body number ten times more than human cells
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 of the microbiome roles
essential for maintaining health
produce some vitamins we cant make
extract nutrients from food
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 to the human microbiome
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
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.
blood, cerebrospinal fluid, synovial fluid, deep tissues
Transient vs. resident organisms
transient- somtimes present
resident- always present
pathogenicity and virulence also depend on?
Pathogenicity/virulence also depends on the host
Definition of pathogen not so certain
Examples where normal flora are source of infection:
periodontitis - overgrowth of particular bacteria in gingival crevices
pneumonia - defenses lowered and microaspirations of pneumococci.
catheter-associated infections - staphylococci
Oral flora includes
bacteria (and archeae) fungi protozoa (eukaryotes) viruses ~700 different species of bacteria are estimated to be present in the oral cavity
Oral habitats
buccal mucosa dorsum of tongue tooth surfaces crevicular epithelium dental appliances
Issues for microbial cells
Nutritional fluxes
Maintaining occupancy
Resistance to damage
Factors modulating oral microbial growth
anatomical features that create areas that are difficult to clean saliva GCF microbial factors pH redox potential antimicrobial therapy diet iatrogenic factors
Factors modulating oral microbial growth- anatomical features that create areas that aredifficult to clean
shape and topography of teeth e.g. fissures
malalignment of teeth
poor quality of restorations (e.g. fillings and bridges)
non-keratinized sulcular epithelium
Factors modulating oral microbial growth-saliva
components?
functions?
mixture of inorganic ions, organic constituents, proteins, glycoproteins (e.g. mucin)
promotes adhesion of bacteria on tooth surfaces, organic components form a coating on tooth surfaces= salivary pellicle
source of food
promotes aggregation of bacteria, facilitating their clearance from mouth
inhibits growth of microbes by non-specific defensefactors
maintains pH
Factors modulating oral microbial growth-
gingival crevicular fluid
flushing microbes out of crevice source of nutrients for microbes maintains pH specific and non-specific defense factors phagocytosis- neutrophils main phagocyte
Factors modulating oral microbial growth
microbial factors
competition for adhesion receptors toxin production metabolic end products negative vs. positive effects congregation
Factors modulating oral microbial growth-local pH, how can it vary
will vary with diet as a result of bacterial metabolism
3 domains of life
eukaryotes, bacteria and arachea
Prokaryotic Cell Membrane
required?
encompasses?
possible internal membranes?
- membranes are an absolute requirement for all living organisms
- plasma membrane encompasses the cytoplasm
- some prokaryotes also have internal membrane systems
The Plasma Membrane contains? orgainzed? symmetry? flex/dynamic?
• contains lipids and proteins
– lipids usually form a bilayer
– proteins are embedded in or associated with lipids
• highly organized, asymmetric, flexible, and dynamic
The asymmetry of most
membrane lipids
• polar ends – interact with water – hydrophilic • nonpolar ends – insoluble in water – hydrophobic
other mem lipids
euk-cholesterol
bac- hopanoid
Membrane proteins
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
• separation of cell from its environment
• selectively permeable barrier
– some molecules are allowed to pass into or out of the cell
– transport systems aid in the movement of molecules
location of crucial metabolic processes
• detection of and response to chemicals inc surroundings with the aid of special receptor molecules in the membrane
Inclusion Bodies, membrane?
• granules of organic or inorganic material
that are stockpiled by the cell for future use
• 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 • sites of protein synthesis • smaller than eucaryotic ribosomes – prokaryotic ribosomes Þ 70S – eukaryotic ribosomes Þ 80S
The Nucleoid
• irregularly shapedregion
• location of chromosome (1, circular shaped)
– usually 1/cell
• not membranembound
nucleoid in actively growing cells
In actively growing cells, the nucleoid has projections; these probably contain DNA being actively transcribed
The prokaryotic chromosome
proteins with it?
• a closed circular, double-stranded DNA molecule • looped and coiled extensively • nucleoid proteins probably aid in folding – nucleoid proteins differ from histone
Unusual nucleoids
• some prokaryotes have > 1 chromosome • some prokaryotes have chromosomes composed of linear double-stranded DNA • a few genera have membrane-delimited nucleoids
Plasmids
relation to chromo?
required?
may carry?
• 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
- shape
- protects from osmotic lysis
- contribute to pathogenicity
- protect cell from toxic substances
Cell walls of Bacteria classes
staining colors?
• 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
gram positive cell wall
gram negative cell wall
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 what bacteria class?
functions?
• found in periplasm of gram-negative bacteria • some of their functions – nutrient acquisition – electron transport – peptidoglycan synthesis – modification of toxic compounds
Exoenzymes
• secreted by gram-positive bacteria
• perform many of the same functions that
periplasmic enzymes do for gram-negative
bacteria
Peptidoglycan Structure
- important component of both gram-positive and gram-negative bacteria
- polysaccharide formed from peptidoglycan subunits
- two alternating sugars form backbone (NAG and NAM) that connects to peptide which may contain some AA not found in proteins
gram-negative vs gram-positive peptidoglycan linkages
gram -: D-ALA to DAP to form cross links
Gram +: peptide interbridge with Gly
both form the meshwork of peptidoglycan
Gram-Positive Cell Walls
•additional content?
- composed primarily of peptidoglycan
* also contain large amounts of teichoic acids, lipotechoic acid may anchor the peptidoglycan to the plasma membrane
teichoic acids composition
• polymers of glycerol
or ribitol joined by
phosphate groups
Gram-Negative Cell Walls
- consist of a thin layer of peptidoglycan surrounded by an outer membrane
- outer membrane composed of lipids, lipoproteins, and lipopolysaccharide (LPS)
- no teichoic acids
Important connections of gram - walls
• Braun’s lipoproteins connect outer membrane to peptidoglycan
• Adhesion sites
– 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) components
• consist of three parts
– lipid A
– core polysaccharide
– O side chain (O antigen)
Importance of LPS
- 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
Components External to Cell Wall
Capsules, Slime Layers, and SLayers
Types of material lying outside the cell wall
– capsules
• usually composed of polysaccharides
• well organized and not easily removed from cell
– slime layers
• similar to capsules except diffuse, unorganized and
easily removed
• glycocalyx
– 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
functions of layers external to the cell wall
- protection from viral infection or predation by bacteria
- protection from chemicals in environment (e.g., detergents)
- motility of gliding bacteria
- protection against osmotic stres
Pili and Fimbriae
size compared
functions?
made of?
• fimbriae – short, thin, hairlike, proteinaceous appendages • up to 1,000/cell – mediate attachment to surfaces • sex pili – similar to fimbriae except longer, thicker, and less numerous (1-10/cell) – required for mating (DNA transfer)
Flagella and Motility
required for motility
Patterns of flagellum arrangement
- 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= anchor – hook= bends structure for motion DIFFERENT IN GRAM +/-
The Bacterial Endospore, resistant to?
• formed by some bacteria • dormant • resistant to numerous environmental conditions – heat – radiation – chemicals – desiccation
An Overview of Eukaryotic Cell Structure
• membrane-delimited nuclei • membrane-bound organelles that perform specific functions • more structurally complex than prokaryotic cell • generally larger than prokaryotic cel
The Endoplasmic Reticulum
what can be made here?
irregular network of branching and fusing membranous tubules and flattened sacs (cisternae – s.,cisterna)
• rough (granular) ER
– ribosomes attached
– synthesis of secreted proteins by ER-associated ribosomes
• smooth (agranular) ER
– devoid of ribosomes
– synthesis of lipids by ER-associated enzymes
• Functions of ER
– 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
• involved in modification,packaging, and secretion of materials
cis- associated with ER
trans-distal portion
Lysosomes
– 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 is the site of?
Mitochondria
• site of tricarboxylic acid cycle activity
• site where ATP is generated by electron transport and oxidative phosphorylation
Mitochondrial structure/ contents of different areas
• outer membrane
• inner membrane
– highly folded to form cristae (s., crista)
– location of enzymes and electron carriers for electron transport and oxidative phosphorylation
• matrix
– contains ribosomes, mitochondrial DNA, and large calcium phosphate granules
– contains enzymes of the tricarboxylic acid cycle and the β- oxidation pathway for fatty acids
The Nucleus, contents/components?
• nucleus
– membrane-bound structure that houses genetic material of cell
• chromatin
– dense fibrous material within nucleus
– contains DNA
– condenses to form chromosomes during cell division
• nuclear envelope
– double membrane structure that delimits nucleus
– penetrated by nuclear pores
• pores allow materials to be transported into or out of nucleus
