Lecture 11 Flashcards
THREE DOMAINS:
Bacteria and Archaea (not subdivided into kingdoms, phyla, classes, etc. Instead they are divided into groups.)
Eukarya
The Archaeans are __ diverse than Bacteria, but are rather interesting as they often live in __
less
extreme conditions
which kingdoms have cell wall
almost all Bacteria
all archaea
some eukarya
Peptidoglycan in cell wall?
only most bacteria
Response to antibiotics?
bacteria Growth inhibited
Unicellular or multicellular
bacteria and archaea unicellular
eukarya Most multicellular, Some unicellular
Shapes and Organization of bacteria and archaea
Variety including coccus, bacillus, spiral
Single, diplo, strepto, staphylo
Shapes and Organization of eukarya
Variety (oval, columnar…)
Organized into tissues in multicellular organisms
Nuclear envelope?
only eukarya
Organelles?
only eukarya
Ribosomes
all kingdoms
Chromosome(s) in kigndoms?
bacteria and archaea: 1 (sometimes 2) circular
eukarya: Multiple linear in nucleus (circular in mitochondria & chloroplast)
Growth at >100°C?
only some archaea
Reproduction of kingdoms
bact and archaea: binary fission
eukarya: Mitosis, meiosis/sexual reproduction
rhizobium meaning
a nitrogen-fixing bacterium that is common in the soil
Phylum Proteobacteria:
rhizobium in plants
Problems in humans: food poisoning, stomach ulcers
Gram negative
Phylum Cyanobacteria:
Photosynthetic bacteria that fix carbon & nitrogen. release of large amounts of toxins. Most species are Gram negative.
Phylum Chlamydiae:
bacterium is the cause of a sexually transmitted infection
Gram negative.
Phylum Actinobacteria:
bacteria that make > 500 antibiotics identified so far. We culture them to make antibiotics. Gram positive.
size of Prokaryotes cells
1-10 µm
Most prokaryotic cells are 0.5–5 µm
Most are not much bigger than an organelle.
Why are prokaryotes everywhere?
Prokaryotes are highly adapted and diverse morphologically
Prokaryotes play crucial roles in ___-.
ecosystems
___ have both beneficial and harmful impacts on humans.
Bacteria
size of eukaryotic cells
10–100 µm
The 3 most common shapes of bacteria?
coccus, bacillus, and spiral
the diverse morphology is an adaptation to
survive in diverse environmental conditions.
can Spirillum be diplo, strepto, staphylo
nope, always single
Generalized cell structure for all prokaryotes
DNA - 1 circular chromosome in the nucleoid region -Multiple plasmids Ribosomes Cytoplasm Plasma membrane Cell wall
chromosome:
DNA + protein
plasmids?
are smaller circular fragments of DNA, that often have genes that code for proteins that make the bacteria resistant to certain antibiotics
are plasmids chromosomes
no
The genes of the plasmid are usually not essential to the ___, but they can increase their __
survival of the host bacteria
ability to survive in the presence of certain antibiotics.
Ribosomes in prokaryotes?
site of translation. Their structure is slightly different from that of ribosomes in eukaryotes.
function of cell wall?
maintains cell shape,
protects the cell and
prevents it from bursting in a hypotonic environment
Bacterial cell walls contain ?
peptidoglycan
Archaean cell walls contain __and __but lack __
polysaccharides
proteins
peptidoglycan
capsule function
This sticky covering and the fimbriae can be used to stick to a surface (ex your teeth), to other prokaryotic cells (to form a colony) or to protect the cell from the immune system of the host it’s invading.
endospores?
some bacterial cells can go into dormancy for CENTURIES, by forming endospores; they come out of dormancy when environmental conditions improve.
Gram-positive bacteria
Gram-positive bacteria have simpler walls with a large amount of peptidoglycan
Gram-negative bacteria
have less peptidoglycan and an outer cell membrane that can be toxic to other organisms.
Gram positive bacteria are stained __, while Gram negative bacteria are stained __.
purple
red
Prokaryotes reproduce quickly by __ and can divide every __
binary fission
1–3 hours
colony ?
A colony is therefore made up of identical cells, unless a random mutation happened during binary fission.
Three factors contribute to the genetic diversity seen in prokaryotes:
- Rapid reproduction: binary fission is fast, so the time to go from one generation to the next (parent→ daughter cells → “grand-daughter cells →…) is short.
- Mutation. Mutation rates during binary fission is low, but because of rapid reproduction, mutations can accumulate rapidly over a short period of time.
- Genetic recombination. Combining of DNA from two sources: horizontal gene transfer.
horizontal gene transfer?
movement of 1 or more genes from 1 species to another. It appears that there has been an exchange of DNA even between the prokaryotic and eukaryotic domains.
vertical gene transfer?
from parent to progeny (offspring), for example, you got your genes from your parents.
Prokaryotes are also diverse in the way they obtain _ and _
energy and carbon.
phototrophs?
obtain energy from light
chemotrophs ?
obtain energy from chemicals
do prokaryotes have organelles
prokaryotes don’t have organelles
Obligate aerobes ?
Facultative anaerobes?
Obligate anaerobes ?
Obligate aerobes require O2 for cellular respiration.
Facultative anaerobes can grow without oxygen but use oxygen if it is present.
Obligate anaerobes use only anaerobic metabolism to make ATP. Some are killed by low levels of O2.
In contrast, anaerobic eukaryotes are RARE.
BACTERIA PLAY CRUCIAL ROLES IN THE __
BIOSPHERE
major role of bacteria?
decomposers
Fix nitrogen ?
ONLY BACTERIA can convert atmospheric nitrogen (N2) to ammonia (NH3). Fixed nitrogen is needed to make amino acids and nucleic acids.
Cyanobacteria: mostly in water.
Rhizobial bacteria fix N2 for plants: N2 in air→ NH3 in the soil or wate
bacteria fix co2 into__ and produce__
Fix CO2 into organic molecules & produce O2: Cyanobacteria through photosynthesis
3 roles of bacteria?
- Decomposers
- Fix nitrogen
- Fix CO2 into organic molecules & produce O2
- Symbiotic relationships
equation of co2 fixation
CO2 + H2O → sugar + O2 (O2 is from the splitting of H2O)
Heterocysts?
specialized cells of cyanobacteria that contain enzymes that fix atmospheric N2 into NH4.
Three types of symbiotic relationships
mutualism, commensalism, and parasitism
Mutualism?
both symbiotic organisms benefit +/+
Commensalism?
one organism benefits while neither harming nor helping other in any significant way +/0
Parasitism
harms but does not kill its host +/- (parasites that cause disease are called pathogens +/-).
Mutualism in plants and bacteria?
rhizobacteria facilitate plant growth directly by either assisting in resource acquisition (fix nitrogen into NH4 and make other minerals available) or modulating plant hormone levels, or indirectly by decreasing the inhibitory effects of various pathogens on plant growth and development. In return, the bacteria get fixed carbon (organic molecules) from plants.
3 types of organisms in an ecosystem
producers, consumers, and decomposers
cyanobacteria are __and some bacteria are __(parasites), most bacteria are ___.
producers
consumers
decomposers
all organisms eventually end up being ___.
decomposed
what do decomposers do
Decomposers (bacteria and fungi) break down and absorb dead organic matter and waste.
Some will decompose living organisms (these are considered parasites)
Give 3 examples of mutualism
- The partnership between nitrogen-fixing bacteria and leguminous plants is one example.
- The bee and the flower.
- The bacteria and the human (digestion)
most __ and __ are decomposers, a few are parasites. In addition, a small number of __, are decomposers.
bacteria
fungi
protists
how do decomposers decompose?
They decompose (break down) organic materials through extracellular digestion: that is they secrete exoenzymes that digest the food. Amylase is an exoenzyme released by many bacteria and fungus that hydrolyzes starch and glycogen into disaccharides. The decomposers then simply absorb the digested particles
Prokaryotes cause about half of ___
all human diseases
basic cell structure of prokaryotes?
cell wall, pilli (like tails on the cell wall), flagellum, cytoplasm, 1 (sometimes 2) circular chromosome in the nucleoid region, plasmid, (prokaryotic) ribosomes, plasma membrane
in terms of function, how is the cell wall of prokaryotes similar to that of the plants
Supports the cell,
maintains its shape,
keeps it from bursting under hypotonic conditions (when the cells are placed in water, they will not take in some much water that they burst, as do cells without walls).
How is the composition of the cell wall of prokaryotes different from that of plants?
The main component of the plant cell wall is cellulose, while it is peptidoglycan for bacteria and another substance for Archaeans
Peptidoglycan is found in all prokaryotic cell walls. true or false
false, only in bacteria
Plasmids are chromosomes made up of DNA & protein. true or false
False. Chromosomes are made up of DNA and proteins. Plasmids are not chromosomes, but simply smaller circular DNA molecules, no protein associated with them.
What is the difference between a Gram-positive and a Gram-negative bacterium? 2 things
1 Gram-positive bacteria have a cell wall that consist mainly of a thick layer of peptidoglycan. There is only a thin layer of peptidoglycan in the cell walls of Gram-negative bacteria.
2 The cell wall of Gram-negative bacteria has two components: (1) a thin layer of peptidoglycan, and (2) an outer membrane (different from plasma membrane) that often contains toxins and provides a barrier to many antibiotics. The cell wall of Gram-positive bacteria has only 1 component; peptidoglycan.
Mechanism of action and effects of Penicillin
Prevents synthesis of cell wall (peptidoglycan cross linking)
and
kills Gram positive bacteria, & to a smaller degree, Gram negative
Mechanism of action and effects of Streptomycin
Binds to prokaryotic ribosomes, prevents protein synthesis
and
kills Almost all prokaryotes (some Archaeans are insensitive)
Explain how mutations can introduce genetic diversity (discuss mutations that are beneficial vs mutations that are detrimental to the species).
Mutations are changes in the nucleotide sequence of the DNA (gene, non-gene regions). If the mutation is beneficial, the offspring will possibly survive better, if negative, the offspring may not survive as well. In either case, the DNA sequence and possibly the phenotype, will be more diverse. (note that for sexually reproducing organisms, this mutation must occur in a germ cell (sperm, egg), for it to be passed down to the offspring)
Explain one way that bacteria can develop a resistance to an antibiotic
Bacteria have one or more plasmids that may contain genes that code for resistance to antibiotics and can be transferred between bacterial cells. Random mutations may also occur & affect the ability of an antibiotic to (ex) enter the bacterial cell.
Almost all bacteria are ?(autotrophic? heterotrophic?)
heterotrophic
Proteins are broken down into ______
amino acids (through the breaking of peptide bonds by proteases).
Fats are broken down into ___and __
fatty acids and glycerol (by lipases).
Starch is broken down into ___________
glucose(by amylases).
DNA & RNA are broken down into ____________
nucleotides (by nucleases).
Consider how we digest our food: our intestinal cells release enzymes into the intestine to break down macromolecules into monomers, which are then absorbed. What then makes us different from fungi?
We ingest then digest; fungi digest then ingest. Because of that, unlike decomposers, we do not release appreciable amounts (some digested materials do probably pass through) monomers into the environment to be used by other organisms.
Where does cellular respiration take place in prokaryotes that make ATP by cellular respiration?
The enzymes and other proteins needed for cellular respiration are found within infoldings of the plasma membrane.
Aside from making ATP, what else do the bacteria use the nutrients for?
They use the monomers to build polymers/macromolecules, including those that make up organelles, as well as enzymes and other molecules that are needed for cell growth, reproduction, repair, maintenance of homeostasis… In other words, these molecules are needed for the very survival of a heterotrophic organism like bacteria.
What is nitrogen fixation?
Nitrogen fixation is the process by which nitrogen in the air (N2) is converted to ammonia (NH3).
Which 2 bacteria do nitrogen fixation?
Cyanobacteria and rhizobium
What is nitrogen needed for?
Nitrogen is used to make amino acids (therefore proteins) and nucleotides (therefore nucleic acids), and is found in other molecules (like chitin).
What is carbon fixation? Which bacterium does it? What is the gas that is released into the atmosphere?
Carbon fixation is the process by which living organisms convert CO2 into organic molecules, most commonly through the process of photosynthesis. Cyanobacteria fix carbon through photosynthesis. It releases oxygen into the atmosphere.
What would happen if decomposition didn’t occur?
1) the accumulation of dead organisms
2) the nutrients (minerals, organic molecules etc) would be locked up in these dead organisms
3) eventually, there would not be any nutrients available for the producers
Give one example of prokaryotes involved in symbiotic relationships; one mutualistic and one parasitic.
mutualistic
+/+ Lichen = fungus + Cyanobacterium (or another photoautotroph like alga).
+/+ Rhizobium in plant roots
+/+ Bacteria (the good ones of course) in the digestive tracts of mammals (including humans)
parasitic
+/- Parasitic: The bacteria that cause diseases like those that cause Lyme’s disease, sexually-transmitted disease etc.
What do you think happens to your intestinal microbes when you take an antibiotic?
It kills those that are susceptible to the antibiotic, along with the pathogens, so if the antibiotic is broad spectrum and kill all Gram-negative bacteria it will kill the Gram-negative gut microbes. In general, the more narrow-spectrum the antibiotic is the less of an impact it will have on your gut microbes.
