Bacteriology Exam 1 Flashcards
The periplasmic space is found only in gram _______ bacteria.
negative
what is the function of the periplasmic space?
assists in nutrient uptake and contains several enzymes for degradation and detoxification
prokaryotic chromosomes
double-stranded, closed, circular, not inside of a nucleus
all of the following are differential media except:
a. chocolate agar
b. Macconkey’s agar
c. blood agar
d. eosin methylene blue agar
A
where do bacteria get their nutrients from?
the environment
Other than the chromosomes, where are genes found in prokaryotes?
on plasmids and transposons
how do bacteria multiply?
by binary fission
what is polycistronic mRNA
may encode several genes - regulated by an operon-based promotor
what do operons regulate
bacterial genes during transcription, translation, or posttranslation
Describe anabolic enzymes
“BUILD UP” Essentially a negative feedback loop - during the synthesis of genes, these enzymes will repress the genes in increased presence of the gene’s final product to prevent waste and overproduction
Describe catabolic enzymes
“BREAK THINGS DOWN” These enzymes are induced when the degraded substrate of the catabolic enzyme is present so they can degrade them. When the substrate is absent, a repressor binds to the operon and blocks the transcription of the gene.
Is the LAC operon a catabolic or an anabolic reaction?
it is a catabolic reaction.
What are the types of horizontal gene transfer?
transformation, transduction, and conjugation
Transduction
transfer of genetic material through viruses
Transformation
cell uptake of free DNA from the environment from another dead bacterial cell (phagocytosis)
conjugation
transfer of genetic material from one bacterial cell to another via cell contact through sex pili
Example of vertical gene transfer
binary fission
Most bacteria get their energy from __________.
Glycolysis
The 2 general methods for ATP production in bacterial cells (which one is best)?
oxidative phosphorylation
substrate-level phosphorylation - best method
Process that uses final electron acceptors other than oxygen
Anaerobic respiration
single-celled, multi-celled, or other? : viruses, fungi, parasites, bacteria
bacteria: single cell, PROK
viruses: other; not a cellular organism
fungi: single or multi, EUK
parasites: single or multi, EUK
What provides support for cellular structure in prokaryotes? Eukaryotes?
Eukaryotes: cytoskeleton
Prokaryotes: cell wall composed of peptidoglycan
what color does gram positive stain
purple
what color does gram negative stain
pink/red
What is another name for peptidoglycan
Murein layer
Is the peptidoglycan layer thicker in gram positive or gram negative?
gram positive
Is an outer membrane found in gram positive, gram negative, or both?
gram negative only
What is found in the outer membrane (LPS layer) of gram negative cells?
Porins, Lipid A, periplasmic space `
What is the repeated pattern of units found in the peptidoglycan of bacteria? What amino acid does it end with?
NAG-NAM-NAG-NAM, and it ends with Alanine
T/F: the peptidoglycan layer is not essential for survival in bacteria
FALSE; it is essential, which makes peptidoglycan a great target for antibiotics.
Function of peptidoglycan
gives cell shape and strength to withstand environmental pressure changes to prevent cell lysis
What does a gram positive cell wall contain?
- a thick peptidoglycan layer
- lipoteichoic and teichoic acids
Example of bacteria with a waxy substance within the peptidoglycan layer that makes it more stubborn to toxic substances
Mycobacterium
Function of the capsule
protects bacteria from the host immune system and forms biofilm to help with attachment
T/F: the capsule functions as an effective permeability layer and adds strength to the cell envelope
False
hairlike structures that extend from the cell membrane
fimbriae or pili
F factor
fertility factor - allow bacteria to perform conjugation
T/F: F positive cells only initiate mating with F negative cells
true
structure responsible for bacterial motility
Flagella
Where do mostly all functions occur that are not conducted by the cell membrane?
the cytosol
Examples of organisms that produce endospores
Bacillus and Clostridium sp.
When would an endospore form (in endospore-forming bacteria)
during harsh physical and chemical conditions and when nutrients are scarce
A systematic process applied to all living entities to classify them based on name to identify organisms by phenotype or genotype
Taxonomy
Variations in gene expression not caused by nucleic acid sequence similarities or differences
Epigenetics
A method for organizing microorganisms into groups or taxa based on similar morphologic, physiologic, and genetic traits
Classification
What is the “gold standard” for bacteria speciation?
the use of 16S rRNA in bacterial DNA hybridization
Classification/Taxonomy hierarchy in order from least specific to most specific
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
What is the difference between vertical and horizontal gene transfer?
Vertical: gene transfer resulting in a new generation (daughter cells)
Horizontal: gene transfer between organisms of the same generation (no new cells result, just transferring genes between already existing cells)
Function of the cytoplasmic membrane in bacteria?
Is it found in gram negative, gram positive, or both?
Present in both; it is heavily laced with various proteins linked to cellular metabolism
Difference between prokaryotic and eukaryotic mRNA?
prokaryotic: polycistronic (produces several proteins that are functionally related)
eukaryotic: monocistronic (produces a single protein)
What is the ideal time of illness that specimens should be collected?
During the acute phase of an illness - within 2 to 3 days for viral infections and before any antibiotics or medicines are given
Which is a preferred method of collection: swabs or tissue/needle aspirates?
Tissue or needle aspirates are preferred if they are able to be obtained.
Should specimens be collected in wooden swabs?
No
What type of swab is suitable for aerobic and anaerobic cultures?
Eswabs
Most specimens should be transported to the laboratory within ________ of collection.
2 HOURS
Specimen transportation guidelines
- transported to lab within 2 hours
- sealable, leak-proof bag with separate section for paperwork
- special preservatives if necessary to ensure organism survival
Boric acid preservative
Used in urine samples
Polyvinyl alcohol (PVA) and buffered formalin for preservatives
used for stool for ova and parasite (O&P) examination
What is holding media? Name 2 examples
Maintains the viability of microorganisms present in a specimen without supporting the growth of the organisms
Ex. Stuart’s medium and Amie’s medium
Anticoagulants as preservation method
Used in specimens to prevent clotting such as blood, bone marrow, and synovial fluid
What type of anticoagulant should not be used for microbiology specimens?
EDTA, Citrate
SPS (sodium polyanethol sulfonate) as a preservative
anticoagulant; used at a concentration of 0.025% because Neisseria and some anaerobic bacteria are particularly sensitive to higher concentrations
Heparin as a preservative method
anticoagulant; commonly used for viral cultures but may inhibit the growth of gram positive bacteria and yeast
What samples should be stored at 4 degrees celsius?
Urine, stool, viral specimens, sputa, swabs, and catheters
How long can serum for serologic studies be frozen for and at what temp?
Up to 1 week at -20 degrees celsius
What temp should tissues or specimens for long-term storage be at?
-70 degrees celsius
What is a requisition slip?
A medical order sent along with the sample from a physician to the lab along with the specimen
Name a few things that should be on a requisition slip (all are listed below)
Name, hospital identification #, age, DOB, sex, collection date and time, ordering physician, nature and source of the specimen, diagnosis (may be ICD-10 code), current antimicrobial therapy
What samples need a direct gram stain?
Samples that are typically sterile and would usually not have bacteria at the site.
What type of specimens would you not do a direct gram stain on?
Throat, nasopharyngeal, or stool (because they typically have bacteria on them regardless)
Nutrient media and (example of one)
Supports the growth of a wide range of non-fastidious microorganisms and are considered nonselective (ex. blood agar)
Blood agar is considered to be _______ and _______ medium.
nutritive and differential
Selective media (and example)
Support the growth of one group of organisms but not another due to inhibitory chemicals found in the medium (ex. MacConkey agar)
MAC
selective media (crystal violet inhibits growth of gram positives) and differential media (lactose fermenting vs non lactose fermenting)
Columbia agar
selective media (Colistin and nalidixic acid inhibit gram-negative growth)
MAC lactose vs non-lactose fermenting colors
pink - lactose fermenting
yellow/clear - non lactose fermenting
enrichment media (and example)
supports the growth of fastidious organisms such as Haemophilus spp (ex. chocolate agar)
Backup broth
examples of some
- allow low number of organisms in an environment to grow compared to agar plates
- allow anaerobes to grow at the bottom of the tube
- allows damaged organisms to grow
ex. brain-heart infusion, tryptic soy brother, thioglycollate broth
What is selection of media for a given specimen based on?
- body site location
2. what pathogens are most likely to cause disease in that body site
beta-hemolysis on BAP
complete hemolysis - visualizes a clear/transparent ring around the colonies on the plate
alpha-hemolysis on BAP
partial hemolysis - visualizes a green/opaque color on the plate
gamma-hemolysis on BAP
no hemolysis occurred - no change around the colonies on the plate
chromogenic agars
produce a pigmented colony to presumptively identify a particular bacteria (ex. MRSA, VRE, Candida)
Aerobes
21% oxygen, 0.03% CO2
Obligate anaerobes
killed in the presence of oxygen, must grow in 5-10% hydrogen, 5-10% CO2, 80-90% nitrogen, 0% oxygen
aerotolerant
do not use oxygen, but are not killed by a small amount
capnophile
(ex. haemophilus influenzae and neisseria gonorrhoeae) require 5-10% CO2 and 15% O2
microaerophile
(ex. campylobacter jejuni and helicobacter pylori) grow in 8-10% CO2 and 5-10% oxygen
Classification of bioterrorist agents
Category A - highest risk
Category B - moderate to low mortality rates and transmission
Category C - emerging pathogens that could be at risk for mass spread in the future
Category A bioterrorism agents
Anthrax, Botulism, Plague, Smallpox, Tularemia, Viral hemorrhagic fevers
Category B bioterrorism agents
Brucellosis, epsilon toxin of Clostridium perfringens, Glanders, Food safety threats
