Bacterial growth and Physiology Flashcards
What are the steps involved in prokaryotic cell division?
- The bacterial chromosome moves to the membrane, which triggers cell division
- Each daughter chromosome is on a different part of the membrane
- As the membrane grows, the daughter cells are pulled apart
- Once the cells are far enough apart, the septum closes off and now you got two #daughter cells
What is the role of transpeptidase in bacterial replication and what happens if there’s incomplete cleavage of the septum?
The peptidoglycan layer has to be pulled apart and re-established in each cell so you use the transpeptidases (penicillin binding proteins) for that
*Antibiotics can stop septation and replication and you can create giant cells instead of having two equivalent daughter cells*
Incomplete cleavage of the septum causes the bacteria to form long chains or clusters
What do you need Ca, Mg, Fe and K for in bacterial growth?
Ca is a chelator, needed for heat resistance for endospores (calcium chelates)
Mg needed to stabilize enzymes
Fe needed for many things including ATP synthesis
K needed for protein synthesis (potassium = protein synthesis)
What is the difference between phototrophs and chemotrophs?
What electron sources are used by lithotrophs and organotrophs?
What carbon sources are used by autotrophs and heterotrophs?
Energy sources:
Light – phototrophs
Oxidation of organic of inorganic compounds – chemotrophs
Electron sources:
Reduced inorganic molecules –lithotrophs (like myself, poor so I can only eat inorganic stuff at reduced prices)
Organic molecules – organotrophs (the rich vegans that only eat organic stuff)
Carbon sources:
CO2 as sole/main source – autotrophs (like Yas and Chimmy O who eat a bunch of carbs/fries and don’t eat no vegetables)
Reduced, preformed, organic molecules from other organisms – heterotrophs (like white people, they be taking everything good and delicious from black folk and reduce it to some preformed raisin in potato salad nonsense)
Why is oxygen toxic to anaerobes?
No SOD and no Catalase in anaerobes so they can’t break down oxygen species to harmless compounds
Describe the difference among thermophilic, mesophilic and psychrophilic bacteria
Some bacteria are thermophiles and can come from hot springs (live in high temps); can’t grow at normal temperatures that cause disease in us coz they like #hot_temps
Mesophilic bacteria tend to cause disease in humans (so they’re normal temps are closer to human ones) and don’t like super high temps so that’s why you have a fever so you can move the temp to un uncomfortable one for the bug
The min temp is kinda cold but not super cold coz #membranes. In a gram neg specifically, if the temp gets too cold, the membrane stops functioning and then it can’t grow anymore
Some bugs will live in environment at colder temperature but become more pathogenic when they get into a warmer human host
The thing that causes the plague normally grows at a flea’s temp (fairly low) but as soon as it goes into the human body, it instantly goes to 37 degrees and becomes invisible (coz we can’t normally recognize it)
Psychrophiles: normally grow at low temperatures
Explain the phases of bacterial growth and what happens at each stage
Exponential phase: bacteria are replicating at their quickest rate
Stationary phase: death rate = reproduction rate
Death phase: lowest reproduction (cell death highest)
Define bacterial generation time
Generation time: the time interval for cells to double their population
g = t/n where
g = generation time (doubling time)
t = time interval (e.g. hours or minutes)
n = number of generations (number of times the cell population doubles during the time interval)
Describe the procedure below
Serial dilutions and you just plate the bacteria and then count backwards
Match the word to the definition:
ASEPSIS
Inactivation or elimination of ALL viable organism and their spores
The state of being free of microorganisms
STERILIZATION
DISINFECTION
SANITIZATION
Process of removing or killing MOST microorganisms on or in a material
A cleaning process which REDUCES pathogen levels to produce a healthy clean environment
ASEPSIS: The state of being free of microorganisms
STERILIZATION: Inactivation or elimination of ALL viable organism and their spores
DISINFECTION: Process of removing or killing MOST microorganisms on or in a material
SANITIZATION: A cleaning process which REDUCES pathogen levels to produce a healthy clean environment
T/F: Germicide = kills vegetative bacteria and some spores (kills all kinds of spores)
What is the difference between a disinfectant and an anti-septic?
GERMICIDE: Substance that kills vegetative bacteria and some spores.
(falsehood. only GERMINATING spores will be kilt)
DISINFECTANT: Substance used on non-living objects to render them non-infectious; kills vegetative bacteria, fungi, viruses but not spores
ANTISEPTIC: Substance used to prevent multiplication of microorganism when applied to living systems. An antiseptic is bacteriostatic in action but not necessarily bactericidal.
Rate the following from most to least resistant to disinfection:
vegetative bacteria
mycobacteria
hydrophilic viruses
lipophilic viruses
bacterial spores
fungi
see below
If you put lipophilic viruses (enveloped) on a phomite (any hard surface), the lipid membrane falls apart (so you won’t be able to transfer a lipophilic virus without its lipophilic envelope)
Vegetative bacteria: when they’re growing, you can give them a host of things to kill em
Mycobacteria and spores are the hardest to kill
Describe the following physical sterilization methods:
Autoclaving
Hot air sterilization
Autoclaving: Pressure and time at heat
The center has to achieve the temperature when autoclaving (esp true when you’re autoclaving something at a large volume);
Sterilizes by moisture, which is good because moisture rehydrates spores so you release them and kill them (can check if you’ve sterilized everything by using spore strip)
(others: see image below)
Describe the following physical sterilization methods
Filtration disinfection
Radiation
Filtration: Dependent on pore size. Everything that goes thru the pore is sterile, everything that is retained isn’t and is disinfected. Size of the pore depends on which bug you want to sterilize (if you want to sterilize a virus, you’d have to use a smaller filter size compared to what you would use for bacteria)
Radiation : give gamma source and keep it under water and put whatever is to be sterilized around the gamma source. Then they pull the source out of the water, irradiate it for however long, then put it back in the water
If the radiation is strong enough, it’ll break the dna and nothing will grow
How is ethylene oxide used to sterilize surgical tools?
Surgical tools sterilized by ethylene oxide so that things don’t rust. Ethylene oxide introduces cross-links into the dna strands
How do use alcohols and halogens to disinfect bacteria?
100% alcohol is not as efficient at disrupting membranes as adding water back to it. That’s why you do 60 to 90% alcohol. Not very good for bugs that need longer contact time for them to be killed
Chlorine disrupts ETC (household chlorine is 3%), normally used at 0.3%. Damaging to metal at high concentrations
What is a biofilm?
**Quorum sensing: when the concentration of bacteria are high enough, the bacteria start secreting molecules and communicate with each other to resist clearance by host immune system (the bacteria grow slower, the antibiotic can’t penetrate as well, the biofilm is too big to be phagocytosed**
What are some examples of biofilm diseases?
see below
