Exam 2 Flashcards
Heterotroph
Use organic molecules as carbon sources
Autotrophs
Use carbon dioxide as their sole or principal carbon source
Phototrophs
Use light (energy source)
Chemotrophs
Energy from oxidation of chemical compounds (energy source)
Lithotrophs
reduced inorganic substances (electron source)
Organotrophs
extracts electrons from reduced organic compounds
(electron source)
What would it mean for an organism
to be a photolithoautotroph?
- Gets energy from light
- Gets electrons from inorganic minerals
- Gets carbon from CO2
Photoorganoheterotroph
- Gets energy from light
- Gets electrons from organic minerals
- Gets carbon from Organic carbon
Chemolithoautotroph
- Gets energy from inorganic chemicals
- Gets electrons from inorganic minerals
- Gets carbon from CO2
- Certain bacteria & Archaea
Chemoorganoheterotroph
- Gets energy from organic chemicals
- Gets electrons from organic minerals
- Gets carbon from organic carbon
Respiration
- Chemoorgantrophic pathway
- Uses electron transport chain
- Aerobic respiration
- Anaerobic respiration
Aerobic respiration
Final electron acceptor is oxygen
Anaerobic respiration
Final electron acceptor is different oxidized molecule such as NO-3 , SO2- , or Fe3+
Fermentation
- Chemoorganotrophic pathway
- No Electron Transport Chain, substrate-level phosphorylation only
- Electron acceptor is an intermediate of the pathway used to oxidize the organic energy source
Amphibolic pathway
Embden Meyerhof pathway can “run in reverse” to convert 2 pyruvate molecules back into a glucose molecule
Embden-Meyerhof Pathway
- Starts with glucose
- Net yield: 2 ATP, 2 NADH, 2 pyruvate
- Amphibolic pathway
Entner-Doudoroff Pathway
- Used by Gram negative bacteria
- Replaces the 6-carbon phase of the Embden-Meyerhof pathway
- Net yield per glucose molecule: 1 ATP, 1 NADPH, 1NADH
Pentose-Phosphate Pathway
- Can operate at the same time as glycolytic pathway or Entner-Doudoroff pathway
- Can be aerobic or anaerobic
- Amphibolic pathway, but does not make ATP
- More of an anabolic role (ribose 5-phosphate builds precursors for amino acids, nucleic acids)
Bacterial Electron Transport Chain: Flexible
- Electron carriers can be replaced or different terminal oxidases may be used
- Located in plasma membrane
Bacterial Electron Transport Chain: Branched
Electrons may enter the chain at several points and leave through several terminal oxidases
Bacterial Electron Transport Chain: Shorter
Fewer protons transported across the membrane and therefore less energy
Dissimilatory nitrate reduction (card 1)
-Use of nitrate as terminal electron acceptor
- making it unavailable to cell for assimilation or uptake
Denitrification
Reduction of nitrate to nitrogen gas (N2)
Anaerobic Respiration (more details)
- Same electron transport chain, but oxygen free
- dissimilatory nitrate reduction
- denitrification
- yields less ATP bc molecules are less electronegative than O2
Fermentation (more details)
- Simpler, produces less ATP than respiration
1. does NOT involve electron transport chain
2. Pyruvate or other derivatgive is final e- acceptor
3. Oxygen not needed
4. Substrate-level phosphorylation of ATP only
Lactic acid fermentation
- Reduction of pyruvate to lactate (lactic acid)
- Used by many species of Lactobacillus
Alcoholic fermentation
- Reduction of pyruvate to acetaldehyde
- then alcohol thru enzyme called alchol dehydrogenase
- Used by yeasts
Mixed acid fermentation
- Excretion of a mixture of acids (that is, acetic, lactic, succinic and formic acids)
- Ex. E.Coli
Butanediol fermentation
- Butanediol is the end product
- Some ethanol, lactic acid and formate are also made
- Ex. Klebsiella, Enterobacter sp.
What’s the difference between
photosynthesis and phototrophy?
Photosynthetic organisms use light energy to ultimately make sugar, while phototrophic organisms may only convert light energy to chemical energy (ATP)
Chlorophyll
Used by cyanobacteria to do oxygenic phososynthesis
Bacteriochlorophyll a,b
Found in purple&green bacteria, anoxygenic photosynthesis
Bacteriorhodopsin
Used by halophilic archaea to capture light energy and use it to fuel proton pump (chemical energy)
Anabolic reactions in microbes
- Cell wall (peptidoglycan)
- Amino acids (enzymes, ribosomes)
- Nucleic acids (reproduction/repair)
- Lipids (membranes, LPS)
Bactoprenol
transports NAG-NAM-pentapeptide units across the cell membrane
Carbohydrate Synthesis
- Complex process
- Bactoprenol; key target for antibiotics
- cross links are formed by transpeptidation
Synthesis of Amino acids
- many precursor metabolites are used as starting substrates for synthesis of amino acids
- carbon skeleton is remodeled
- amino group and sometimes sulfur are added
Steps of synthesis of amino acids
- Inorganic nitrogen assimilation
- sulfur assimilation
- Amino acid biosynthetic pathways
- Anaplerotic reactions
Transaminases
Nitrogen can be transferred to other carbon skeletons by this
Assimilatory Nitrate Reduction
- Used by bacteria to reduce nitrate to ammonia
- then incorporate it into an organic form
Nitrogen Fixation
- Reduction of nitrogen (N2) to ammonia (NH3)
- catalyzed by nitrogenase
- found only in a few bacteria and archaea
Sulfur assimilation
- Sulfur needed for: synthesis of amino acids and synthesis of several coenzymes
- Sulfur obtained from: either external sources or intracellular amino acid reserves and inorganic sulfate
Amino acid biosynthetic pathways
- used in the synthesis of multiple amino acids
- A single precursor metabolite can give rise to several amino acids
Anaplerotic reactions
- regeneration of intermediate molecules
- carbon skeletons used for: biomass & extract energy from carbon-carbon bonds
- citric acid cycle intermediates are used
Lipid Synthesis
- Necessary for all membranes
- most bacterial and eukaryal lipids contain fatty acids
Lipopolysaccharide synthesis
- important component of gram negative bacterial outer membrane structure
- combines lipid and carbohydrate anabolic pathways: Lipid A (core branch) & O-antigen (branch)
What cellular structures are unique to bacteria?
Peptidoglycan cell walls, 70s ribosomes
Which type of bacterial fermentation is used in the dairy industry?
Lactic acid fermentation
Which phototrophic pigment molecule is found in archaea?
Bacteriorhodopsin
Name some terminal electron acceptors in anaerobic respiration
Nitrate, sulfate, iron
Biocide
Antimicrobial agents that control microorganisms
Sterilization
Process in which all living entites are destroyed or removed from an object
- sterilant is the chemical agent
Disinfection
Killing, inhibition, or removal of disease causing microorganisms
Sanitization
reduction of microbial population to levels deemed safe by public health standards
Antisepsis
destruction of microbes on living tissue
Antiseptics
Chemical agents applied to tissue to kill or inhibit growth
Depth filter
fibrous materials that have been bonded into a think layer filled with narrow channels
Membrane filter
Porous membranes with defined pore sizes that remove microorganisms
High-efficiency particulate air (HEPA) filters
- used in laminar flow safety cabinets
- exclude 99.97% of particles
- Covid-19 showed this filter to be effective
Moist heat
- destroys viruses, fungi, and bacteria by degrading nucleic acids, denaturing proteins and disrupting cell membranes
- boiling will not destroy endospores and does not sterilize
autoclave
- device used to steam sterilization
- above 100C (15 psi)
pasteurization
- controlled heating at temperatures below boiling
- process does not sterilize, but does kill pathogens and slows spoilage
Ultraviolet radiation
- 260nm wavelength most lethal
- causes thymine dimers preventing replication and transcription
chemotherapy
application of chemicals to kill microorganisms
Cidal agents
- agent that kills
Static agents
- agents that inhibit growth
Phenolics
- denature proteins, disrupt cell membranes
- used in hospital settings
Halogens
- Iodine, oxidizes cell components and proteins
- Used as a skin antiseptic
Chlorine
- Oxidizes cellular components, destroys vegetative bacteria and fungi
- bleach
Metals
- inactive proteins, only copper and silver used
- copper sulfate treats algal blooms in lakes
Quaternary ammonium compounds
- Detergents that have broad spectrum antimicrobial activity
- effective disinfectants, but cannot kill endospores
Broad-spectrum antibiotics
kills a wide variety of bacteria
Narrow-spectrum antibiotics
specifically kill one or a few kinds of bacteria
Penicillins
- inhibit peptidoglycan synthesis
- Ex. penicillin, amoxicllin
Cephalosporins
- inhibit peptidoglycan synthesis but broader spectrum than pencillins and cephalosporins
- used to treat severe infections
- Ex. imipenem, meropenem
Glycopeptides
- inhibit the synthesis of peptidoglycan by binding to amino acids in the cell wall
- Ex. Vancomycin (“drug of last resort)
Aminoglycosides
- Block the A site of the ribosomes so no new amino acids can be added
- Ex. Streptomycin, neomycin kanamycin
- inhibit the small (30s) subunit
Tetracyclines
- prevent tRNAs from binding to ribosomes
- Ex. minocycline, doxycycline
- inhibit small (30s) subunit
Macrolides
- bind to 50s subunit, preventing ribosomes assembly
- Ex. Z-pak, erythomycin
Lincosamides
- Bind 50s subunit
- Ex. Clindamycin, lincomycin
Fluoroquinolones
- target protein of the bacterial replication machinery (gyrase and topoisomerase) blocking DNA pol III
- Ex. Ciprofloxacin, levofloxacin
Folate synthesis inhibition
- requires folate (Vitamin B9) to complete DNA replication
- sulfonamides compete w other intermediates in pathways that produce folate, inhibiting synthesis
Kirby-bauer method
- disks with antibiotic at known concentration placed onto inoculated plate
Zone of inhibition
Clearance area in a kirby-bauer method
E-test
- strip with a gradient of antibiotics is placed on inoculated plate
- where ellipse intersects the scale shows the dosage at which bacteria is susceptible
Methicillin-resistant staphylococcus aureus (MRSA)
responsible for many cases of post surgical sepsis and death
Clostridium difficile (C-diff)
- causes extreme diarrhea which can be fatal
- difficult to treat because spores remain resistant and can germinate, causing relapse
reverse transcriptase inhibitors
- used to treat HIV and AIDS
Amphotericin B
- binds to ergosterol (similar to cholesterol), dissolves cell membrane
- anti-fungal drug
Azoles
- block synthesis of ergosterol
- anti-fungal drug
- Ex. ketaconazole
Anti-malarial drugs
- chloroquine, lariam, artimisin used in combination to destroy malaria infected red blood cells
- resistance growing across the world
Anti-giardia drugs
- Metronidazole
- effective against Trichomonas vaginalis
Overcoming drug resistance
- Tighter controls over use of antibiotics in animal feed
- Limiting over-prescription of antibiotics to patients
- Combination therapies (multiple drugs)
- targeted biological therapy
Phages
viruses that prey on bacteria
Reproductive strategies
- reproduce by binary fission
- reproduce by forming a bud or multiple fission
- must replicate and segregate the genome prior to division
Bacterial cell cycle
- period of growth after the cell is born
- chromosome replication and partitioning
- Cytokinesis, during which a septum and daughter cells are formed
FtsZ
Protein that establishes divison site at mid-cell, defines plane of division
Peptidoglycan synthesis
- plays a role in determine cell shape
Coccus (shape)
- peptidoglycan forms at central septum
- FtsZ localization placement involved
Elongasome
rod complex
MreB
protein scaffold on cytoplasmic face of cell membrane
Crescentin
protein that localizes asymmetrically, giving rise to vibrio shape
Bacterial growth
- referred to as population growth rather than growth of individual cells
Batch culture
incubated in a closed vessel with a single batch of medium
Lag Phase
- bacterial growth curve
- cell synthesizing new components
- replenish spent materials
- Adapt to new medium or conditions
- eventually, cells replicate DNA, increase in mass, divide
Exponential phase
- bacterial growth curve
- rate of growth and division is constant and maximal
- population is uniform
Stationary Phase
- bacterial growth curve
- closed system, growth ceases
- viable cells remains constant
reasoning for stationary phase
- Nutrient limitation
- limited oxygen availability
- toxic waste accumulation
- carrying capacity reached
Death phase
- bacterial growth curve
- number of viable cells declines exponentially
- nutrient deprivation and build up of waste causes harm
Long-term stationary phase
- bacterial growth curve
- bacterial population continually evolves
- process marked by successive waves of genetically distinct variants
- natural selection occurs within a single culture
extremophiles
Grow under harsh conditions that would kill most other organisms
Halophiles
- require NaCl at a concentration > 0.2 M
Extreme halphiles
- require salt concentrations 3M-6.2 M
Salt in halophiles
- accumulate K and Cl in cytoplasm
- proteins need high salt levels
Salt out halophiles
- keep salt ions outside of cell
- synthesizes compatible solutes that do not interfere with growth
Acidophiles
- growth best between pH 0-5.5
- pump protons (H+0
Alkaliphiles
- growth best between pH 8-11.5
Psychrohiles
0 to 20C
Psychrotrophs
0 to 35C
Mesophiles
20 to 45C
Thermophiles
45 to 85C
Hyperthermophiles
85 to 100C
Adapting to temperature
- protein structure stabilized by a variety of means
1. more H bonds
2. more proline, less flexible peptides
3. Chaperones aid in folding - membranes stabilized by variety of means
1. more saturated, more branched, higher molecule weight
2. ether linkages, resistant to hydrolysis
obligate aerobe
requires O2
Obligate anaerobe
usually killed in presence of O2
Microaerophile
requires 2-10% O2
Facultative anaerobes
doesn’t require O2 but grow better in its presence
Aerotolerant anaerobes
grow with or without O2
Reactive oxygen species (ROS)
- oxygen reduced
- superoxide radical
- hydrogen peroxide (H2O20
- hydroxyl radical
Aerobes produce protective enzymes
- Superoxide dismutase (SOD)
- Catalase
- Peroxidase
Biofilms
- Slime enclosed communities of microbes
- ubiquitous in nature in water
- can be formed on any conditioned surface
Extracellular polymeric substance (EPS)
- microbes reversibly attach to conditioned surface and release polysaccharides, proteins and DNA
Emergent properties
the whole system is greater than the sum of its individual parts
Quorum sensing
- bacterial cells communicate via small molecules that diffuse the environment
- number of microbes must be present and participating
Culture medium
Solid or liquid mixture of nutrients and other compounds
defined/synthetic medium
each ingredient can be defined with a chemical formula
Complex media
Contain some ingredients of nonspecific chemical composition
Supportive media
- sustain growth of many microorganisms
- trypic soy brother and agar
Enriched media
- supportive media supplemented with special nutrients
- blood agar
selective media
- allow the growth of particular microorganisms, while inhibiting the growth of others
- gram negative bacteria grows on bile salts, gram positive bacteria cannot
Differential media
- distinguish among different groups of microbes and permit identification of microbes
replication fork
where DNA is unwound