Final Exam Flashcards
Traits shared by ‘prokaryotes’
-70S ribosomes
- Complex cell walls
*-Majority have circular genomes in compact nucleoid
- Share many metabolic traits
Differences between Bacteria and Archaea
- rRNA gene sequences
- Membrane lipids (ether-linked isoprenoid lipids
forming mono/bilayers) - pseudopeptidoglycan
- Domain Archaea lacks known pathogens
Archaea grow within a wider range of
- temperature
- osmolarity
- pH
- other environmental conditions
Bacterial drug resistance mechanisms
- Efflux pump (multidrug resistant
- Target modification spontaneous mutation)
- Secreted - degrative enzymes - enzymatic alteration
How does horizontal gene transfer for antibiotic resistance spread?
Conjugation of plasmids. Using sex pilus 2. Transduction by bacteriophages 3. Transformation uptake of dna released by lysis
‘What practices underlie our problem of extensive
antibiotic resistance?
Innapropriate/overuse
Patient non compliance
Non prescription purchase
Agricultural use
‘What could lead to the development of a superinfection
‘Broad spectrum anti microbial
What strategies can counter antibiotic resistance ?
Chemistry modification of existing drugs
Integrated resistance monitoring
Vaccine R and D
Combbjnation therapy
Prohibit agriculture use
What do mycorrhizae do? ___ w
➢ Fungal hyphae surround/enter
Impact car
Bon cplant roots → enhance plant’s uptake of water anD minerals while obtaining sugars from plants
➢ critical to reforestation efforts
Ye modelling
Booster shots to increase
memory cells and the level of immunity
Unvaccinated surrounded by a 70% vaccinated/immune
population are protected by
herd immunity
The most distinctive structure of
archaea is their
ether-linked
membrane
ether-linked
membranes can form in a
_____ and use ___ glycerol
monolayer, L
Archaea lack ____ molecules
peptidoglycan
some _____ archea who
have pseudopeptidoglycan
methanogens
Genomes of archaea resemble
those of bacteria in __ ____ and ____
gene size and
density
what of archaea is similar with those of eukaryotes
DNA and RNA polymerases
and transcription factors are
similar to those of eukaryotes
eukaryoticarchea with methanogens
Serve a key energetic role in ecosystems
by providing for anaerobic H2 removal
through the production of methane
Haloarchaea supplement their metabolism
with light-driven ion pumps, called
bacteriorhodopsin
Methanogens can use a diversity of substrates to produce
methane (4)
Carbon dioxide:
Acetic acid:
Methanol:
Methylamine
Methanogens grow in
soil, under
permafrost, in animal digestive tracts,
and in marine floor sediment
major source of methanogens
is
landfills
methane
hydrates
Methane produced by methanogens deep underground is trapped in ice
Protozoa are ____- that are single-celled heterotrophs.
Protozoa are protists that are single-celled heterotrophs.
mycoses
illness caused by fungi
Most molds are made of
hyphae
the three types of hyphae are
septate, coenocytic, pseudohyphae
important yeast pathogens
Candida albicans,
Cryptococcus neoformans
moulds are involved in
composition of organic
matter, allergies, asthma, Aspergillus
fumigatus
Basic structures of moulds
Spores (or conidia) are produced in
chains on a conidiophore (a form of
aerial hyphae
spores have
Sterol-containing membrane
fungal cell wall inner
Inner cell wall is relatively conserved,
made up of chitin and branched β-1,3-
glucan
fungal cell wall outer
Many yeasts (including Saccharomyces
and Candida species) have an outer cell
wall comprised of the polysaccharide
mannan and mannoproteins
35
Symbionts
Form critical symbiotic relationships with plants (i.e. mycorrhiza), algae
(i.e. lichens), and insects
invasive pathogens (in immunosuppressed
patients) with very high mortality rates
Candida, Cryptococcus, Aspergillus42
protists are
polyphyletic and highly divergent
The algae are
autotrophic protists
algae perfom
Perform oxygenic photosynthesis via chloroplasts some produce toxins
algae have
Rigid cell walls: cellulose +
glycoprotein layer …
OR sometimes silica
protozoa are the predators of the microbial world, engulfing prey through _____
(heterotrophs).
phagocytosis
protozoa lack
cell walls
Different methods of locomotion:
➢ Cilia beat like oars and are not like prokaryotic pili
➢ Flagella move like fishes’ tails unlike prokaryotic flagella
➢ Amoeboid movement using pseudopodia → evolved separately in different lineages
Primary algae
ancestral pre-
eukaryote cell engulfed an
ancestral phototrophic
cyanobacterium, which became
the chloroplast
Secondary algae - engulfment
of a primary phototrophic
endosymbiont (e.g. algae) by a
mitochondria-containing
eukaryotic cell
Distinguishing feature: the
chloroplast is surrounded by
two membranes
Secondary algae
engulfment
of a primary phototrophic
endosymbiont (e.g. algae) by a
mitochondria-containing
eukaryotic cell
Distinguishing feature: the
chloroplast is surrounded by
two membranes
Oxidations and reductions of
inorganics
lithotrophy and anaerobic respiration
The Winogradsky column is stable for years with only
light and gas exchange
The Winogradsky columns are maintained by
1.Phototrophic microbes
2. Heterotrophic microbes
3. Lithotrophic bacteria & archaea
4. Anaerobically respiring microbes
5. Fermentative microbes
lithotrophic archaea are
major _______
producers beyond the
_______ (aphotic
zone)
marine primary, euphotic zone
oligotrophic
low conc of minerals and plants
eutrophic
High conc of minerals and plants
The Great Plate Count Anomaly
solation/identification and
viable plate counting will not give an accurate characterization of
community composition
metagenomics
is most often used to characterize microbial communities → culture-independent DNA purification and
sequencing (rRNA gene (SSU (16S)) or shotgun (sequencing
everything))
microbes increaswe
Increase [essential nutrients]
that limit growth of primary
producers
Biotechnological applications of the microbes:
Harnessing the microbes:
➢ *biotechnology, biocontrol & bioremediation
➢ food, beverage and pharmaceutical industries (antibiotics & vaccines)
Bioremediation
the use of life forms (often microbial) to
degrade pollutants to nontoxic forms
Through oxidation for energy generation
➢ Or reduction, in fermentation or as terminal
electron acceptors (anaerobic respiration)
Most often exploiting the phenomenon that collectively,
heterotrophic microbes degrade (oxidize) everything
Urban wastewater treatment plant
- Physical separation
- Aerobic heterotrophy
- Anaerobic heterotrophic digestion
➢ CH4 from methanogens: burned, or used for energy
Fermentation
anaerobic process that occurs in some
HETEROTROPHIC bacteria and in yeasts -> no electron
transport chain (ETC) involved
Myriad of desirable
and undesirable
products (off flavours)
Alcoholic fermentation in beer and wine
Fungal metabolism: heterotrophs and saprophytes are not
selective in what their secreted enzymes degrade nor the
nature of their organic substrate
Spoiled foods from other heterotrophs
– anaerobic, toxigenic, endospore-forming
Gram positive bacterium Clostridium
botulinum
Molds
- causes intoxication or infant infections
Unseen dangers: Food contaminated with pathogens can lead
lead to
food-borne infections (bacterial and viral) or
intoxications (bacterial)
-The Gram positive bacterium
Listeria monocytogenes is
ubiquitous in the environment
The organism is a facultative
psychrophile
➢ it can grow at 4° C
➢ primarily a problem in ready-
to-eat foods
Virions
are the extracellular, and
infectious, form of the virus
filamentous viruses have
helical
symmetry
classification of viruses
damiy, sub family, genus, species
Viruses are classified or identified based on a combination of
criteria:
Nature of genome – including nature, shape,
strandedness and whether it is segmented
2. Capsid symmetry
3. Envelope - +/-
4. Size of viral particle
5. Host range
Viral infection and reproduction:
- attachment
- penetration
- uncoating
4.biosynthesis - assembly
- release
- maturation
( A PUB ARM
Bacteriophage life cycle
Attachment to specific host cell receptors
* Phage genome is injected through the cell wall and membrane
and the capsid is shed
* receptors play a role in normal cell function
Bacteriophages can undergo two different types of life
cycles
- Lytic cycle
- rapid phage replication & lyses / kills host
- lytic phages, e.g. T2, T4 - Lysogenic cycle
Temperate phage infects & inserts its
DNA into host chromosome
- activated to excise and follow lytic
life cycle by certain triggers
- e.g. phage λ
Coronavirus virion
- Spike protein (S) – trimers provide specificity for cellular entry
receptors - Envelope (E) – ensure incorporation into viral particle during
assembly - Membrane (M) – ensure incorporation into viral particle during
assembly - Nucleocapsid (N) - +ssRNA encapsidation
Culturing Viruses requires
a host cell
Two types of Bacteriophage culture systems
* batch culture (in liquid)
* isolated plaques on a bacterial lawn (on a plate
Cyticidal effects of viral
replication
destruction of host cells in
culture results in the
formation of plaques
vaccine types
Live attenuated
Inactivated/killed
Subunit (Toxoid, polysaccharide,
conjugate)
NRM
non-replicating mRNA
SRM
self-replicating mRNA
Paul Ehrlich
proposed the principle of selective toxicicity-Used (small molecule) screening,
still used today
Sir Alexander Fleming
penicillin, produced by the fungus
Penicillium notatum, in 1928
Drugs target critical and unique aspects of the
bacterial cell physiology:
they are selectively
toxic
➢ Cell wall (i.e. peptidoglycan)
➢ Cell membranes (e.g. G-negative OM)
➢ DNA synthesis (e.g. DNA gyrase)
➢ RNA synthesis
➢ Protein synthesis (e.g. ribosomes)
Chemical modifications to a “first generation” antibiotic may
increase spectrum of
activity, acid stability, and/or thwart some mechanisms of resistance (e.g. β-lactamase)
Combinatorial Therapy
Two treatments (e.g. Antibiotic A + chemical B)
* Additive – Both have a (probably) separate effect
* Antagonistic – More growth
* Synergistic – Both have a (probably) related effect
Rhizobia + legumes
The rhizobia (e.g. Rhizobium spp.) form nodules on legume roots and fix nitrogen
only in this symbiosis (“diazotrophy”)
Digestion in ruminants
plant fiber → cellulose (fungi)
➢ Cellulose → Sugar + H2 + CO2 (cellulolytic bacteria)
➢ (H2 and CO2 microbial fermentation products are used by
methanogens** to produce methane)
The rumen is
anaerobic
➢ Anthropogenic
(human made) GHG
ratio of human to microbial cells
1:1.4
Physical barriers
epithelium, mucociliary blanket,
hair/eyelashes, skin (shedding)
Mechanical barriers
blinking, mucociliary escalator, swallowing,
coughing, sneezing, urination, diarrhea
microbiome
bacteria of skin, upper respiratory tract,
gastrointestinal tract, and genitourinary tract
Chemical barriers
Tears, toxic lipids (oils), sweat, lysozyme in tears, saliva & mucous
Koch’s Postulates
establishing the causative agent of infectious disease
Koch developed the technique
of single colony isolation on
solid media
Break in/find a key: stick to, breach the epithelial barrier (and subsequent tissues), exploit an
existing entry system
Adhesins - pili, capsules, LPS help attach/ resist dislodging; viral
coat/envelope proteins facilitate cell attachment AND penetration
❖ Degradative enzymes - bacterial exotoxins,
Break in/find a key: stick to, breach the epithelial barrier (and subsequent tissues), exploit an
existing entry system
❖ rely on a physical/health breakdown or indwelling device
Mycobacterium tuberculosis
hijacks phagocytic cells
(alveolar macrophages) → resists phagocytic killing,
multiplying in alveolar macrophages → chronic
inflammation gives tubercles 24
“immunopathogenesis”
average person inhales __ microbes per minute
8
AZT
recognized by, blocks reverse
transcriptase activity
Fuzeon
inhibits fusion of HIV envelope with host cell
plasma membrane
Key leukocyte players:
T lymphocytes – variety of subtypes
➢ coordinate, regulate (TH, Treg); provide cell-mediated immunity (TC);
differentiate into memory cells
B lymphocytes
➢ Produce plasma cells → antibodies; produce memory cells
virtually limitless antigen structures (and
their epitopes) can be recognized
from previous exposure**
recognizes microbiota but tolerates them in
their normal body sites
Acquired immune response always includes ____ activation
\ B cell \
May also
secrete IgM in
T-cell independent activation
epitope presented on MHCI of infected cell or MHCII of APC
mchci
Antibodies opsonize antigens:
Neutralize viruses
➢ Neutralize toxins
➢ ↑ phagocytic efficiency through Fc binding
IgM
first responder to a new epitope; pentameric → 10 antigen-binding sites
IgG
higher affinity; plasma cells more long-lived; produced after chromosomal
splicing and class switching in IgM-producing B cells
