Intro to Bacteria Flashcards
Gram-Positive Bacteria
thick peptidoglycan in cell wall
have lipoteichoic acid
Gram-Negative Bacteria
thin peptidoglycan layer, have outer membrane (lipopolysaccharide)
Lipopolysaccharide
lipid A component or endotoxin. Harmful to host. Polysaccharide component contributes to antigenicity, may provide protective immunity and used as a component of vaccines
Flagella
filamentous structure on bacterial surface used for motility. Number and arrangement used for identification
Pili/Fimbria
small thread-like structures on bacterial surface that facilitate adherence to the host tissue through specific receptors and contribute to antigenicity
Capsule
outer coating made of polysaccharide. Help bacteria evade phagocytosis
Endospores
highly resistant dormant form on bacteria produced when exposed to adverse conditions. Found in gram-positive bacteria.
Flagella Significance
Virulence Factor
Fimbriae Significance
virulence factor, components of diagnostic tests and vaccines
Capsule Significance
virulence factor, component of diagnostic tests and vaccines
Endospore Significance
virulence factor, diagnosis, vaccines
Growth Phases
Lag, Log, Stationary, Death
Aerobic Bacteria
require oxygen for survival
Microaerophile
requires environment with low amount of oxygen
Capnophile
thrive in an environment high in CO2
Obligate Anaerobe
killed by oxygen
Aerotolerant Anaerobe
do not require oxygen but can survive in oxygen environment
Facultative Anaerobe
oxygen not required but can be used
Exotoxins
produced inside pathogenic bacteria as part of their growth and metabolism. Are secreted into surrounding medium following lysis. Gram-positive, heat labile
Endotoxins
lipid portion of lipopolysaccharide that are part of outer membrane of the cell wall of gram-negative bacteria liberated when the bacteria die. Heat stable, can induce inflammation
Superantigens
produced by pathogenic microbes. Bind and cross-link indiscriminately to MHC Class II molecules on the macrophages and T helper cell receptor. Results in oligoclonal T cell activation and massive cytokine release
Biofilm
microbes come together in masses and cling to surfaces, produce extracellular polymeric substances and take in nutrients and form biofilm. Reduce antimicrobial susceptibility
Quorum Sensing
molecular communication systems to synchronize the expression of certain genes
Plasmids
smaller circular DNA preset in bacteria. May carry genes for antibiotic resistance, toxins, capsules, and fimbriae and can mediate transfer of the virulence factors through conjugation, transformation
Bacteriophage
viruses that attack bacteria. Carry virulence factors and transfer through transduction
Classification of Bacteria
staining properties, metabolic properties, biochemical characteristics, fatty acid profile, DNA sequencing
Phylogeny
science dealing with the evolutionary relationship between living organisms based on sequences of DNA, RNA, and protein. 16s ribosomal gene
Microbiome
body contains 10x more bacteria than cells. Play a role in immunity, mood, obesity, chronic inflammation
Pathogenesis
complex interactions between host, pathogen, and environment. Mechanisms by which pathogens cause disease
Virulence Factors
traits that cause disease but are not found in isolates of the same species that lack the ability to cause disease
How bacteria cause disease
- changing normal physiology by direct damage to host cells (toxins)
- deplete host’s nutrients by using them
- immune response (inflammation) to the infectious agent
- impose a combination of above effects
Mechanism of Disease
- entry into host
- evade host defenses
- colonize host systems
- multiply
- exert damage to host
- transmission to other hosts
Colonization
the presence of bacteria on a body surface without causing disease
Infection Outcomes
- subclinical/chronic infection
- infection, disease, recovery
- infection, disease, death or disability
- infection, disease, persistence
Endoflagella
spirochetes have endoflagella, which are in the periplasmic space
Significance of Bacterial Metabolism
bacterial organism varies in their growth rate, need for oxygen and nutrients. These traits can be used for bacterial cultivation and identification
Significance of Bacterial Toxins
Increases the virulence and pathogenicity
Biofilm Significance
promote chronicity and reduce antimicrobial penetration and susceptibility
The purpose of being a pathogen
to enhance transmission
Extracellular Pathogen
Survive outside the cell
Obligate Intracellular Pathogen
survive only inside the cell
Facultative Intracellular Pathogen
survive inside and outside the cell
What are most bacteria
extracellular pathogens
Sequence of events in bacterial pathogenesis
- Entry into the host
- Evade host defenses
- Colonize the host systems
- Multiply
- Exert damage in the host
- Transmission to other hosts
Infection
the invasion of a host organism’s tissues by disease causing organisms
What are the differences between a eukaryotic and prokaryotic organism?
- Prokaryotes lack a nucleus, eukaryotes have a nucleus
- Prokaryotes do not have membrane-bound organelles, eukaryotes do
- Prokaryotes are typically smaller than eukaryotes
- Prokaryotes have a complex cell wall, eukaryotes have a basic one when present
- Eukaryotes have a cytoskeleton, prokaryotes do not
- Prokaryotes have small 70s ribosome, eukaryotes have larger 80s ribosome
- Prokaryotes have a single circular chromosome, eukaryotes have multiple linear chromosomes with histones
- Prokaryotes divide by binary fission, Eukaryotes by mitosis
- Eukaryotes reproduce by binary fission
What is the unique component of Mycobacterium
mycolic acid
How do flagella relate to bacterial virulence?
providing motility towards host targets
What are the differences between endotoxins and exotoxins?
- An exotoxin is produced by gram-positive bacteria. An endotoxin is produced by gram-negative bacteria.
- Exotoxins are secreted into medium following lysis. Endotoxins are released after bacteria die and cell wall falls apart.
- Exotoxins are heat-labile. Endotoxins are heat resistant
- Endotoxins exert effects on target cells. Exotoxins induce inflammation
Can bacteria transfer virulence factors, and how do they do it? Some examples?
Yes, through plasmids in processes such as conjugation, transformation. Ex: tetanus neurotoxin Staphylococcus enterotoxin carried by a plasmid
Pathogen
microbe that can cause disease
Pathogenesis
mechanisms by which bacteria cause disease
Virulence
degree of pathogenicity
What are the relative differences between obligate, primary, and opportunistic pathogens?
Obligate pathogen does not need a lot of microbes, does not need host predisposition, is very virulent, and causes distincy disease
Primary pathogen needs more microbes and somewhat host predisposition, is moderately virulent, and causes distinct disease.
Opportunistic Pathogen needs a lot of number, more host predisposition, is not very virulent, and causes non-specific disease.
What is the iceberg effect in disease epidemiology?
Most of the effects of a disease are unseen. So epidemiologists need to combat not only the visible consequences of disease, but the invisible as well
Cell Wall Component unique to gram positive bacteria
lipoteichoic acid
cell wall component unique to gram negative bacteria
outer membrane containing lipopolysaccharide
Cell wall component unique to mycobacteria
mycolic acid
Measurement of Bacterial Growth
- colony counting
- turbidimetry
- spectrophotometry
- flow cytometry
