Chapter 4 Flashcards
What are those that must be supplied from the environment for microbial nutrition?
Essential Nutrients
What are some examples of Macronutrients?
Carbon, Oxygen, Ca2+ etc
What are some examples of micronutrients?
Trace elements such as ZN
What are three things that are required for microbial nutrition?
Essential Nutrients
Macronutrients
Micronutrients
What do autotrophs do?
fix CO2 and assemble into organic molecules (mainly sugar)
What do heterotrophs do?
use performed organic molecules
What type of organism obtains energy from chemical reactions triggered by light?
Phototrophs
What type of organsim obtains energy from oxidation-reduction reactions?
Chemotrophs
What type of organism uses inorganic molecules as a source of electrons?
Lithotrophs
What type of organisms use organic molecules?
Organotrophs
What is generated when chemical energy is used to pump protons outside of the cell?
Membrane potential
What forms because of the H+ gradient plus the charge difference?
Proton motive force
What can the potential energy that is stored do?
- transport nutrients
- Drive flagella rotation
- Make ATP by the
F1F0 ATP Synthase
What makes up 79% of Earth’s atmosphere but is unavailable for use by most organisms?
N2
What possess nitrogenase, which converts N2 to ammonium ions(NH4+)?
Nitrogen Fixers
What oxidizes ammonia to nitrate(NO3-)?
Nitrifiers
What converts nitrate to N2?
Denitifiers
What are the three ways that selective permeability is achieved?
1. Substrate-specific
carrier proteins
(permeases)
2. Dedicated nutrient-
binding proteins that
patrol that
periplasmic space
3. Membrane-spanning
protein channels or
poresWhat helps solutes move across a membrane from a region of high concentration to one of lower concentration?
Facilitated Diffusion
What is the name for those in which energy released by a driving ion moving down its gradient is used to move a solute up its gradient?
Coupled transport systems
What is the name for when two molecules travel in the same direction in a coupled transport system?
Symport
What is the name for when the actively transported molecule moves in the direction opposite to the driving ion in a coupled transport system?
Antiport
What is the largest family of energy-driven transport system?
ABC Transporters
What are specialized molecules secreted to bind ferric ion and transport it into the cell?
Siderophores
What is the process that uses energy to chemically alter the substrate during its transport?
Group Translocation
What is an example of group translocation in bacteria?
PTS (phosphotransferase system)
What are the two main types of culture media used to grow bacteria?
- Liquid or broth
- Solid (usually gelled
with agar)
What are the two ways pure colonies are isolated?
- Dilution Streaking]
2. Spread Plate
What is dilution streaking?
a loop is dragged across the surface of an agar plate
What is a spread plate?
1. Tenfold serial dilutions
are performed on a
liquid culture
2. A small amount of
each dilution is then
platedWhat type of media is nutrient rich but poorly defined?
Complex media
What type of media contains only those nutrients that are essential for growth of a given microbe?
Minimal defined media
What type of media is a complex media to which specific blood components are added?
Enrichment Media
What type of media favors the growth of one organism over another?
Selective media
What type of media exploits differences between two species that grow equally well?
Differential Media
What is MacConkey medium?
- Growing only Gram
Negative bacteria - LAC(+) or LAC(-)
What are specific nutrients not required by other species?
Growth Factors
Why can we still not know how to grow some microbes in the lab?
Some species have adapted so well to their natural habitats that we still do not know how to grow them in the lab
How can microorganisms be counted directly?
by placing dilutions on a special microscope slide called a Petroff-Hausser counting chamber
What does a fluorescence-activated cell sorter (FACS) or flow cytometer do?
an electronic technique that not only counts but also separates populations of bacterial cells according to their distinguishing properties
What is defined as being capable of replicating and forming a colony on a solid medium?
a viable bacterium
What is the pour plate method?
a way to count viable cells
Microorganisms can be counted indirectly via?
biochemical assays of cell mass, protein content, or metabolic rate
What are three rules for colony counting?
- You cannot measure cell size or growth
phase. - Same species produce a single colony by
multiple cells - You always underestimate the cell number
How do most bacteria divide?
binary fission
What is an asymmetrical way that bacteria divide?
budding
What is a rate of increase in cell numbers or biomass, and is proportional to the population size at a given time?
growth rate
If a cell divides by binary fission, the number of cells is proportional to?
2n
What does n represent?
the number of generations
What is the generation time?
the time it takes for a population to double.
What is Nt = N0 x 2n?
- Nt is the final cell number
- N0 is the original cell number
- n is the number of generations
- This is the formula for binary fission
What type of growth never lasts indefinitely?
Exponential Growth
What are some characteristics of a batch culture?
- closed system(in a flask nothing can go in
or out) - The simplest way to model the effects of a changing environment is to culture bacteria
What do the changing conditions in the batch culture affect?
greatly affects bacterial physiology and growth
What does batch culture illustrate?
the ability of the bacteria to adapt to their environment
What are the phases in a bacterial growth curve?
- Lag Phase
- Log Phase
- Stationary Phase
- Death Phase
What happens in the lag phase?
Bacteria are preparing their cell machinery for growth
What happens in the log phase?
Growth approximates an exponential curve
What happens in the stationary phase?
Cells stop growing and shut down their growth machinery while turning on stress responses to help retain viability
What happens in the Death phase?
Cells die with a “half-life” similar to that of radioactive decay, a negative exponential curve
What is quarum sensing?
-The regulation of gene expression in
response to fluctuations in cell-population
density
-Signals other cells to do an action
-happens late in the log phase (to tell the
cells to stop growing)
What culture is when all cells in a population achieve a steady state?
continuous culture
What does continuous culture allow for?
detailed study of bacterial physiology
What is the main characteristic of Continuous culture?
Open system
What is a chemostat?
- an example of a continuous culture
-ensures logarithmic growth by constantly
adding and removing equal amounts of
culture media.
What in the human body is similar to chemostat?
the gastrointestinal tract
What does a continuous culture graph look like?
see slide 53
What are specialized, surface-attached communities called?
biofilms
What are characteristics of biofilms?
can be constructed by one or multiple species and can form on a range of organic or inorganic surfaces.
True or false. Bacterial biofilms grow when nutrients are plentiful.
True
What happens to biofilms when nutrients become scarce?
individuals detach from the community to forage for new sources of nutrients.
What is a benefit of multiple bacteria forming a biofilm together?
-act as a multicellular organism
What is a common example of a biofilm?
teeth plaque
Chemical signals enable bacteria to communicate(via quorum sensing) and in some cases can form…?
biofilms
What are three attributes that go into biofilm development?
- adherence of cells to a substrate
- formation of microcolonies
- the formation of complex channeled
communities that generate new planktonic
cells
What are the 5 steps in biofilm development?
- Attachment to monolayer via flagella
- Microcolonies
- Exopolysaccharide production (EPS)
- Mature biofilm
- Dissolution and dispersal
Repeats again
What do sessile(nonmoving) cells do in a biofilm do?
-chemically talk to each other in order to build microcolonies and keep water channels open
What causes bacteria to undergo complex molecular reprogramming that includes changes in cell structure?
environmental stress
Clostridium and Bacillus reproduce by?
species can produce dormant spores that are heat resistant
What is an asymmetrical cell division process that produces a forespore and ultimately an endospore?
An 8-hour genetic program initiated by starvation
What does Anabaena differentiate into?
heterocysts
What does differentiating into heterocysts allow it to do?
fix nitrogen anaerobically while maintaining oxygenic photosynthesis
- Dipicolinic acids + Ca2+
~ 10% of dry wt.
-Reduce water contents in the endospore
(dehydration)
- Small Acid-Soluble Proteins (SASP)
- to protect spore’s DNA
- To provide energy for germination
What is the enzyme that causes N2 fixation?
- nitrogenase (oxygen-sensitive)
