Bacteria - Metabolism, Transmission, Relationships, Infection Mechanisms, and Invasion Flashcards
What pH do most bacteria grow best at?
a neutral pH (7)
In regards to CO2, what type of environment do bacteria grow better?
in an environment containing a small amount (5-10%) of CO2
In regards to oxygen, what are the byproducts of the metabolic processes of some bacteria?
highly toxic forms of oxygen such as 2O2 and H2O2
In regards to oxygen, how do bacteria live in it?
they either need to have a means of detoxifying oxygen or they need to grow in environments where oxygen does not occur
What is 2O2 broken down by?
superoxide dismutase
What is H2O2 broken down by?
catalase and peroxidase
What are the types of bacteria (in regards to oxygen, i.e anaerobe etc.)
strict aerobes, strict (obligate anaerobes, facultative anaerobes, and microaerophiles
What is an example of a strict aerobe?
pink eye in cattle
What is an example of a microaerophile?
leptospira
What are the sources of infectious agents of bacteria?
animals and humans, and inanimate nature
What is the general normal flora for bacteria?
skin, mouth, stomach, small intestine, large intestine, etc.
Define incubation period.
period from the time of infection until clinical signs appear
What is a convalescent carrier?
those who have recovered from their illness but remain capable of transmitting to others
What is a contact carrier?
when you acquire the microorganism from contact with the infected
What is subclinical infection?
an infection that is nearly or completely asymptomatic
What are some sources of infection?
droplet, dust, ingestion, contact, wounds, injection, via genital tract, transplacental, umbilical, and nosocomial
What are heterotrophs?
organisms incapable of using either light or inorganic compounds as an energy source or of using CO2 as a sole carbon source
What are saprophytes?
heterotrophs that live on dead or decaying organic matter - most pathogenic bacteria
What is a commensal relationship?
doesn’t cause disease
What is a opportunist relationship?
normally harmless in their usual environment but cause disease when they gain access to other sites or tissues
What is an obligate pathogen?
a parasite that cannot complete its lifestyle without exploiting a suitable host
What are Koch’s postulates?
- the organism must be regularly isolated from cases of the disease
- it must be grown in vitro in pure culture
- a pure culture should produce the typical disease when inoculated into a susceptible animal
- the same organism must be isolated from the experimentally induced disease
What are the three components of colonization of mucosal surfaces?
association, adhesion, and invasion
What is association?
localization of bacteria on or near the cell surface - they may associate with mucus or exudates, establish small numbers of noncovalent bonds with the surface or respond to chemotactic factors
What is bacterial adhesion?
stable, irreversible attachment of a bacterium to a mucosal surface
What is bacterial adhesion usually between?
specific surface proteins of the bacterium and carbohydrate-containing molecules on the eukaryottic cell surface or glycocalyx
What are hemagglutinins?
molecules which mediate agglutination of erythrocytes that may also function as adhesions
What is adhesion greatly affected by?
the electrostatic charge and hydrophobicity of the cell surfaces that interact
What is the Derjaguin-Landau and Verwey-Overbeek (DLVO) theory?
two rigid bodies of like charge approach each other they are affected by attractive and repulsive forces, which vary independently with the distance between the bodies
Over what distance is there a net force of attraction?
> 10nm
Over what distance is there net repulsive force?
1 - 10 nm
Over what distance is there a strong attractive force?
distance of less than 1 nm
What happens to the presence of repulsive force as the radii of curvature decreases?
the repulsive force is less and may be able to bridge the intermediate zone of repulsive forces and establish a stable receptor-ligand bond
What cations help bridge the intermediate zone?
Fe3+ and Ca2+
What can proteinaceous adhesions be divided into categorically?
those with fimbrial morphology and those lacking definite shape and size
Describe fimbrial adhesions.
filamentous structures that vary from 2-7 nm in diameter and which extend up to 4 micrometers from the bacterial surface
Describe type 1 fimbriae.
closely related to F6 fimbriae
relatively rigid structure, a uniform cross-sectional diameter, and an axial hole
subunits are arranged as a helical structure
tends to aggregate into highly ordered, parallel bundles
Describe nonfimbrial proteinaceous adhesions.
adhesions that lack a definite structure and often take the form of secreted proteins or proteins associated with the outer membrane
What is an example of a species that has a nonfimbrial proteinaceous adhesion?
staphylococcus aureus
How does lipoteichoic acid bind to eukaryotic cells?
by interacting with a fibronectin receptor
What is expression of bacterial adhesions affected by?
the conditions under which the organisms grow both in vitro and in vivo
When do type 1 fimbriae grow?
in cultures of organisms grown in static broth culture beyond late log phase but they are not produced in cultures grown on agar media
What do mucosal cells of host tissues have on their surfaces and what do they do?
glycoproteins and glycolipids which act as receptors for hormones, nutrients, and a variety of other molecules as well as carbohydrate receptors that provide binding sites for bacterial adhesions and toxins
What is an extracellular parasite?
organisms that reside out of eukaryotic cells
What is a facultative intracellular parasite?
an organism that has the capacity to grow and survive both inside and outside of eukaryotic cells
Do extracellular parasites or facultative intracellular parasites live longer?
facultative intracellular parasites
What is an obligate intracellular parasite?
parasites that can only grow within cells
Provide an example of a parasite that can gain entry by trauma or puncture.
Clostridium tetani
Provide an example of a parasite that can gain entry by endocytosis.
Salmonella typhimurium
Provide an example of a parasite that can gain entry via receptor mediated endocytosis.
Chlamydia psittaci
Provide an example of a parasite that can gain entry via uptake by antigen sampling sites.
Salmonella sp
Provide an example of a parasite that can gain entry via disruption by cytotoxins.
Salmonella sp
Provide an example of a parasite that can gain entry via direct penetration.
Leptospira
Which of the types of invasion is not a true invasion?
trauma or puncture
Explain the process of endocytosis.
eukaryotic cells invaginate and engulf the bacteria in a membrane-bbound vacuole that is similar to the phagocytic vacuole of neutrophils and macrophages
What specific structure is required for endocytosis?
contractile proteins
