Microbiology: A Focus on Bacteria, Fungi, and Viruses Flashcards
How do “bad” pathogens arise from human microbiome
dietary changes
stress
antibiotics
True/false: Majority of pathogens are non-pathogenic
true
What do pathogens do to help them survive?
They constantly evolve by either losing or gaining traits over time
What is the incubation period
The time it takes the pathogen to enter the body and show the first symptom to appear
What does the incubation period depend on
health of host
growth rate of pathogen
degree of exposure
What is the timeline of infection
incubation period –> onset of illness –> period of invasion –> convalescent period
What are the different types of infections
Acute
Chronic
Latent (persistent)
What is an acute infection
Symptoms develop quick
Clears quickly
Host has immunity for reinfection
ex. strep throat
What is chronic infection
Symptoms develop slowly
Can last months to years
ex. tuberculosis
What is latent (persistent) infection
Illness never goes away
It becomes formant in the body and can be awakened with low immunity
ex. syphilis, typhoid, fever, etc.
Carriers: the host may not show symptoms but they spread it to others
What is horizontal transmisson
person to person (horizontal)
ex. blood, saliva, stds, urine
What is vertical transmissoin
Mother to baby via breast milk, delivery, placenta
What is a vector
An animal or arthropod that caries a pathogen and can transfer it to humans
ex. rabies virus transmitted by animal bite
What is virulence?
the degree of pathogenicity of a pathogen (bacteria, fungi, or virus) and is determined by its ability to invade and multiply within the host causing disease
They grow and thrive at the expense of the host
what is a strict pathogen
always causes disease
What is an opportunistic pathogen
part of normal microbial flora
takes advantage of a weakened immune system
caused by the disruption in the microbial flora
breached barrier introduced by a wound
Bacterial Characteristics shapes
Maintained by cell wall of bacteria composed of peptidoglycan
No nucleus –> chromosome forms a structure called a nucleoid
No membrane-bound organelles (prokaryotic)
What are the main shapes of bacteria
cocci
bacilli
spiral
pleomorphic (no defined shape)
What is the cocci shape
Spherical bacteria
What are the different variations of cocci?
Single organisms (cocci)
Pairs (diplococcus)
Chains (streptococcus)
Clusters (staphylococcus)
Tetrads
Sarcina (cube of eight cocci)
What is bacilli
Rod shape
What are the variations of bacilli
Single (bacilli)
Double (diplobacilli)
Chain (streptobacili)
Palisades
What is the intermediate shape between coccus and a bacillus
coccobacilli
What are the shapes of spiral bacteria
Vibrio
Spirillum
Spriochete
What is vibrio
curved or comma-shaped rod
What is spirllum
Thick, rigid spiral
What is spirochete
thin, flexible spiral
What is pleomorphic
do not have any characteristic shape
can change their shape
also can be a combination of shapes
What cell retains crystal violet from iodine
gram +
What cell does not retain crystal violet and appears transparent
gram -
Which cell has a thick multi-layered peptidoglycan layer
gram +
Which cell structure contains lps
gram -
What is LPS
only produced by gram (-)
Consists of lipid and carbohydrate
Helps bacteria cause disease
What are cell wall components
LPS (only in gram -) and peptidoglycan (sugar and amino acids)
which cell type has an outer membrane that prevents crystal violet penetration
gram (-)
Which cell develops resistance more quickly
gram (-)
Which cell is more resistant to antibodies due to impenetrable cell wall
gram (-)
Which cell lacks peptidoglycan
gram (-)
What are acidophiles
bacteria that grow optimally at pH values around 2
What are alkalophiles
only grow well at pH values near 10
Aciduric (acid tolerant)
Can survive acidic conditions but not necessarily grow under those conditions
Psychrophiles
Prokaryotes that grow very poorly at temperatures above 15 celcius
Thermophiles
thrive at 100 degrees C
What are the components of a bacterial cell structure
Capsule
Cell wall
Cytoplasmic membrane
Pili
Flagella
Nucleoid
Cytoplasm
Ribosomes
What is capsule
covers the outer layer of the cell wall
composed of polysaccharides
mediates attachment of bacterium to host tissues
can inhibit phagocytosis by neutrophils and macrophages –> virulence factor for some bacteria
Strep mutans
one of the causative agents of dental caries
attaches to tooth surfaces via a capsule
What is slime layer
some bacteria have a loosely adherent colloidal material that they secrete
usually similar to the capsule
What is a pili (aka fimbriae)
Extend from cell surface
Pili: long hair-like tubular microfibers
Responsible for: attachment and transfer of DNA & motility
only in gram (-) only!!
What is the flagella
extend from interior cell body
Responsible for: motility, also sense certain temperature and chemicals/metals
present in both gram + and -
Bacterial Growth Curve phases
lag phase –> exponential (log) phase –> stationary phase –> death phase
What is the lag phase
initial phase characterized by cellular activity BUT NOT GROWTH
cells increase in size, but no cell division
Exponential (log) phase
cells divide by binary fissions & metabolic activity high
Which bacteria growth phase are antibiotics and disinfectants most effective in?
Exponential (log) phase
Stationary phase
Bacterial cell growth reach a plateau
Number of dividing cells equal the number of dying cells
No overall population growth
Death phase
Number of living cells decreases exponentially
Population growth experiences sharp decline
Bacterial spores
gram (+) bacteria only form spores
especially under adverse environmental conditions
What is the importance of spores
structure of spore protects its DNA from intense heat, radiation, and attack by most enzymes and chemical agents
So resistance to environmental factors –> can exist for centuries
Difficult to decontaminate with standard disinfectants or autoclaving
Aerobic bacteria
require oxygen for basic survival, growth, and reproduction
Anaerobic
don’t require oxygen for growth
Fermentation
Anaerobic conditions only
Conversion of pyruvate to various end products (ethanol and lactic acids)
True/false: aerobic and anaerobic conditions both involve glycolysis
True
Which cell has peptidoglycan and what does peptidoglycan do
gram (+)
Induce fever/inflammation
What does LPS do? (low vs. high doses)
Low doses: activates immune response and triggers fever
High doses: extreme fevers, septic shock, skin lesions (fatal)
Two ways bacteria cause disease
release of exotoxins
bacteria inhibit phagocytosis of immune cells
release of exotoxins (polypeptides)
receptor-binding proteins that cause cell death or change in function
Cytolysis bursting of host cell from osmotic pressure
What type of bacteria releases exotoxins
gram - and gram +
What do exotoxins do
releases: enzymes, gas, acids, toxins
toxins: cause cell lysis and can cause degradation of tissue by immune response
Can be encoded on a plasmid or a bacteriophage
Transformation
introduction, uptake and expression of foreign genetic material
Conjugation
Transfer of DNA via plasmid from a donor cell to a recipient cell
Involves pilius
Transduction
bacterial DNA is moved from one bacterium to another by a virus
Quorum sensing
bacteria’s way to communicate
Fungi
diverse group of free-living eukaryotic micro organnisms
may be unicellular or multicellular
Fungi in our body
controlled by competent immune system and multiplies when conditions are favorable
obligate intracellular parasites
viruses
Are viruses alive
me dont think so because”
do not reproduce, do not maintain metabolism to gain energy on their own
Different virus structures
Naked capsid virus or enveloped virus
What is naked capsid virus (non-enveloped)
typically more virulent
usually cause host cell lysis
cell lysis= most common exit mode from host cell
Does not have extra lipid membrane
Antibodies are generally sufficient for protection against these infections
True/false: Non-enveloped capsid virus is more resistant to extreme pH, heat, dryness, and simple disinfectants
true yuhh
How does naked capsid virus spread
spread on fomites, hand to hand, and by small droplets
Where can naked capsid virus grow
can survive in the gastrointestinal system because of their resistance to low pH and bile detergents
Characteristics of enveloped virus
typically less virulent
don’t always cause cell lysis during cell exit
contain an outer membrane that surrounds the capsid –> can use host cell membrane itself to assemble their membrane –> process avoids cell lysis and helps enveloped viruses escape from host’s immune system
Which type of virus is relatively less sensitive to environmental conditions
enveloped virus
what virus can spread in large droplets and secretions or by organ transplantation and blood transfusion
enveloped virus
Virus classification is based on
size, morphology, nucleic acid, disease they cause, means of transmission
Morphology of a virus is based on
size and shape
Chemical composition and mode of replication
may consist of DNA or RNA
may be single or double stranded
may be linear or circular
Characteristics of DNA viruses
mostly double stranded
replication occurs in the nucleus
has to be transcribed prior to being synthesized into proteins
Exception: a few DNA viruses can replicate in cytoplasm because they carry polymerases
DNA –> RNA –> mRNA –> proteins
Characteristics of RNA viruses
Mostly single stranded
replication occurs in the cytoplasm
can use its RNA to immediately synthesize proteins
RNA –> mRNA –> Proteins
What is a positive strand of RNA
RNA virus that serve as mRNA and can immediately be translated into proteins
RNA/mRNA –> proteins
What is a negative strand of RNA
Viral RNA must first be transcribed into mRNA then can be translated into proteins
RNA –> mRNA –> proteins
What are retroviruses
reverse normal transcription
reverse transcriptase will transcribe the RNA from the virus into DNA and then incorporates it into the host’s cell
DNA <– RNA
Viral Replication APURAM
study on slides for more detail lol
Attachment
Penetration
Uncoating
Replication
Assembly
Maturation
Release
