New User Special Price Expires in

Let's log you in.

Sign in with Facebook


Don't have a StudySoup account? Create one here!


Create a StudySoup account

Be part of our community, it's free to join!

Sign up with Facebook


Create your account
By creating an account you agree to StudySoup's terms and conditions and privacy policy

Already have a StudySoup account? Login here

1.4 Evolution cont'd. & 1.5 Prokaryotes Part 1

by: Gail Chernomorets

1.4 Evolution cont'd. & 1.5 Prokaryotes Part 1 BIOL 251

Marketplace > University of Nevada - Las Vegas > BIOL 251 > 1 4 Evolution cont d 1 5 Prokaryotes Part 1
Gail Chernomorets

GPA 3.2

Preview These Notes for FREE

Get a free preview of these Notes, just enter your email below.

Unlock Preview
Unlock Preview

Preview these materials now for free

Why put in your email? Get access to more of this material and other relevant free materials for your school

View Preview

About this Document

Week 3 notes Notes from 09/13 & 09/15
Medical Microbiology
Kurt Regner
Class Notes
25 ?




Popular in Medical Microbiology

Popular in Department

This 14 page Class Notes was uploaded by Gail Chernomorets on Monday September 19, 2016. The Class Notes belongs to BIOL 251 at University of Nevada - Las Vegas taught by Kurt Regner in Fall 2016. Since its upload, it has received 75 views.


Reviews for 1.4 Evolution cont'd. & 1.5 Prokaryotes Part 1


Report this Material


What is Karma?


Karma is the currency of StudySoup.

You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 09/19/16
09/13 & 09/15 1.4 Evolution cont’d. Natural Selection  Defined as - force or factor that shapes populations  Changes allele frequencies  Gradual process over time  Heritable traits become either more or less common within a population  Differential reproduction - change in phenotype within a same species  Imagine a genetically diverse population of bacteria is exposed an antibiotic - bacteria constantly accumulate random mutations; happens during DNA replication - just by dumb luck some mutations confer resistance to the antibiotic ex. beetles and bird Influenza A  Evolved resistance to the antiviral drug, amantadine - first used in 1966  Since 2008, the CDC has concluded that nearly all (91-100%) influenza A strains were resistant to amantadine  Viruses aren’t alive - have a high mutation rate - matter of time before they become resistant **How do you interpret the 98p4 data? - not resistant - regular strain is resistant and will survive Review  Bacteria, Archaea and viruses are genetically diverse  Many alleles for every gene  Adaptations are selected during natural selection - antibiotics - antiviral drugs - host’s immune system - new carbon source - °C, Pa, [Na ]  Differential adaptations - beneficial adaptations would allow survival, making them the natural selection Two Experiments that Demonstrate the Importance of Mutation and Natural Selection in the Evolution of Bacteria  Lederberg experiment 1952  Lenski experiment 1988-present Lederberg experiment  Investigated whether or not mutations occurred before or after natural selection  Bacteria growth on agar plates without an antibiotic  Colonies transferred via replica plating to a medium with an antibiotic (penicillin) - natural selection  replica plating - used velveteen to cover container and made a “stamp” with the original plate so when transferred to new agar it was identical to the original  Natural selection identify the mutation  Answer - mutations occur all the time  Results of experiment - the majority of the colonies did not grow on the medium with penicillin - those cells did not have mutations for resistance - suggests that random mutations occurred before natural selection and not in response to it  Also washed the original plate with penicillin to make sure that the colonies were resistant before the transfer  The wash confirmed that the mutations occurred before exposure to the antibiotic and not afterward  Thousands of random mutations were generated during the replication of the bacterial DNA  Mutations that conferred an advantage were identified by natural selection (antibiotic) - antibiotic physically attach to cell ** Remember, all populations have genetic variation/diversity  Even individual colonies are made up of many cells that are not genetically identical - evolution depends on inherited traits  Adaptations are identified during differential reproduction Arctic permafrost  Demonstrates random mutations occur all the time  Communities of resistance mechanisms of 5,000 years of age  Clinical levels of resistance  Results demonstrated that antibiotic resistance genes were functionally diverse prior to the anthropogenic use of antibiotics - Contribute to the evolution of natural reservoirs of resistance genes Lenski experiment  Investigated mutation, change in phenotype in a long-term evolution experiment  Starting in ’88, E. coli strains were grown in minimal medium containing 139 μm glucose and 1700 μm citrate - required for iron acquisition and not a carbon source  Every day 1 mL of the culture was transferred to a 99 mL of fresh medium (1/100) - flasks with general growth medium - glucose is the source of carbon - citrate in medium to acquire iron (usually E. coli can’t eat citrate, but after a while one population started to eat it) E. coli in Experiment  6.6 generations per day/2,423 per year  Strong selective pressure for fast growth in order to out compete the other cells for glucose  After 14 years of generation, citrate consuming (cit+) strains began to appear - cause? - Ability to consume citrate (cit+) required several mutations, but the order of appearance is unknown  Typical E. coli cant eat citrate  cit- strains were not eliminated since they consume glucose and can coexist with the cit+ - if ran out could go back to glucose Mutations  Random and appear during DNA replication  Bacteria have a much greater mutation rate than eukaryotes - for speed, give up accuracy  A short generation time = lots of mutations 7 8 - 10 -10 mutations/12 hours  Natural selection identifies potentially useful mutations - useful mutations = adaptations - the ability to catabolize citrate occurred after thousands of generations of random mutations and constant selective pressure Horizontal Gene Transfer Use by Bacteria and Archaea  HGT shifts the allele frequency - acquiring alleles from different groups  HGT is a mechanism of microbial evolution  Acquire DNA from another cell  Same or different species - not a factor of choice  Transformation - chromosomes from one bacterial cell enters a new cell  Conjugation - 4 cells exchange DNA  Transduction - virus picks up DNA from one cell, lands in another cell and injects DNA  Acquired DNA recombines into the chromosome - genes could potentially be expressed Transformation  Bacteria take up foreign DNA from the environment - sensor proteins and DNA are brought inside  Consequences can be that new alleles are acquired - new traits/characteristics can be conferred  Cells that acquire DNA are known as competent - really good at absorbing DNA  Occurs all the time in the microbial world  Antibiotic resistance (+) = functional (-) = non-functional - sites of crossing over (recombination) - met+ - resistant  can synthesize methionine - met- - susceptible  cannot synthesize methionine Conjugation  Bacterial sex  Transfer of genetic material between bacterial cells that are temporally joined  The donor cell transfers DNA to the recipient cell  A sex pilus from the donor pulls the 2 cells together - protein filament or fiber that one cell makes and attaches to another cell and pulls it in  the ability to form a sex pilus and transfer DNA requires fertility (F) factor gene(s) found either on the bacterial chromosome or on a plasma - recipient has to have protein that is compatible  Conjugation tube connects conjugation pilus and are not the same structure as a sex pilus Transduction  Viruses  Occurs when phage picks up piece of bacterial chromosome by mistake  The bacterial DNA is transferred from one host to another by the phage during infection  Infected bacterial cell making viruses and explodes because too much of the infected DNA is inside Why is this important? Why should I care about this?  Antibiotic resistant bacteria kill people - 27k in US yearly Ex. begins with sensitive organism and resistant organism. Expose to vancomycin. Sensitive organisms are killed. Resistant organism survives. Resistant cells multiply in absence of competition. - allele changed due to natural selection  cell that is resistant E. coli resistant to 2 last resort antibiotics Colistin  Not generally used  Toxic to kidneys  Last line of defense for E. coli Carbapenem  Inhibits cell wall formation  Was resistant to bacterial enzymes that degraded similar compounds  Last line of defense for E. coli Vancomycin  Prevented chains from coming in  Effective against gram-positive bacteria  Physically bind to amino acids and prevent them from working  Thick peptidoglycan cell wall outside of membrane  Made up of: - NAM (N-acetylmuramic acid) - NAG (N-acetylglucosamine)  Chains of NAM and NAG cross linked by peptide chains (amino acids)  Prevents peptidoglycan synthesis in gram positive bacteria by binding to D-alanine-D-alanine chains associated with the NAM/NAG units  Stops synthesis of the long polymers of NAM and NAG that form the backbone strands of the bacterial cell wall  Prevents the backbone polymers that do manage to form from cross-linking with each other  Mechanisms to block binding for vancomycin resistance - random mutations changed the last alanine to lactate and vancomycin us unable to bind - in other strains, a mutation changed an enzyme so has the ability to degrade vancomycin ** These strains are resistant to vancomycin - patients die from vancomycin-resistant bacteria Triclosan  5-chloro-2-(2,4-dichlorophenoxy) phenol  Antibacterial soap (recently been removed from), detergent, toothpaste, mouthwash, deodorants  Also added to the surface of many toys and clothes  Originally developed to disinfect surgical equipment and scrubs, hospital gowns - FDA removed because increases resistance to triclosan  Binds to a group of enzymes needed to synthesize fatty acids including membrane phospholipids ** There is no data indicating that triclosan-soaps are more effective than regular soaps Novel resistance mechanism to triclosan that suggests HGT  Evolution in action  Shifted allele frequency with beneficial adaptation ** Viruses have the highest mutation rate  Bacteria grow faster and tolerate a much greater mutation rate than eukaryotes  Mutations are constantly occurring in all genes  Many antibiotics work by physically binding to an enzyme or part of the bacterial cell  Other antibiotics bind to ribosomes and stop translation  A simple change in the shape on an enzyme or ribosome confers resistance - change can be as simple as 1 or 2 amino acids Review  Random mutation(s) occur constantly  Mutation is stabilized in the population due to overuse of antibiotics  New allele confers an advantage under selective pressure  New allele moves via HGT  Result is antibiotic and triclosan-resistant bacterial pathogens 1.5 Prokaryotes Part 1 Bacteria and Archaea comprise nearly half of all biomass on Earth  All habitats that support plants and animals have abundant populations of Bacteria and Archaea  Bacteria and Archaea also exist in habitats too extreme for plants and animals  Prokaryotes outnumber all eukaryotes by 10,000:1 - >10 bacterial cells are present in 1.0 g of soil  Bacteria inhabiting a healthy human adult outnumber human cells by a ratio of 10:1 - low end of estimate  Tremendous diversity - between bacteria and archaea - greater than the differences among animals Ex. sponge and elephant - part of our microbiota Prokaryotes  Bacteria and archaea  Found everywhere  Term becoming obsolete  Ubiquitous  Physiologically diverse  Aerobes, anaerobes, facultative anaerobes  Commensals (mutualistic relationship; coinhabit), symbionts (coindependent), pathogens (minority of bacteria)  Animal and plant life is completely dependent upon prokaryotes **No Archaea are pathogens Idea of Microbiology Community  Term prokaryote is controversial  Microbiologists do not care for the term prokaryote - before the nut  Originally used to describe organisms without: - membrane bound nucleus - membrane bound organelles - a cytoskeleton ** didn’t have the same “stuff” as eukaryotes Nucleoid  Means nucleus-like  An irregularly shaped region within the cell of a prokaryote that contains all or most of the genetic material  Described as lacking a membrane to distinguish it from the eukaryotic nucleus - there are bacteria with a membrane enclosed nucleoid - some prokaryotes have membrane bound organelles Gemmata  True bacterium  Membrane bound nucleoid  Gram-negative bacteria Membranes  Do not have nuclear pores (no nucleus) - not equal to an eukaryotic nucleus  Demonstrates the tremendous diversity among bacteria - highlights the term prokaryote is becoming obsolete  Some bacterial cells are divided into 2 or 3 compartments by membranes  Pirellulosome - ribosome-containing space Riboplasm - where translation occurs - where ribosomes are  Paraphoplasm - ribosome-free space - cellular function is unknown - metabolic activity occurs - some have third region Gemmata and Anammox  3 regions defined by membranes - nucleoid bound by a membrane - riboplasm - paryphoplasm Anammoxosome + -  Anammox bacteria convert NH 4 (ammonia) and NO (nit2ite) to N 2nitrogen) under aerobic conditions  Occurs in the anammoxoxome - reaction occurs here Intracytoplasmic compartment with a bilayer membrane Not exactly same as organelles in eukarya Bacterial Microcompartments  Protein shell for storage or sequestering a particular enzymatic reaction - referred to as bacterial organelles  Many bacteria store excess carbon as poly-β-hydroxybutyrate within a microcompartment Cyanobacteria  Also have carboxysomes - rips apart CO 2  Have internal membranes that resemble photosynthetic thylakoids in plant chloroplasts - support the theory of endosymbiosis  Protein spheres containing RuBisCo the enzyme required for CO 2 fixation  Photosynthetic bacteria - take CO a2d put into sugar  into carboxysomes Bacterial Cell Structure Terms (Some Archaea)  Most bacteria, but not all have a cell wall (peptidoglycan) - exterior to membrane  Pili - short protein fibers - adherence and conjugation  cells want to be next to  Flagella - protein tubes used for locomotion  can have one to twenty  Glycocalyx/Slime layer - polysaccharide gel - adherence and protection from immune system - exude sticky, sugary complex - glycocalyx – a little - slime layer – a lot  sticking organisms to cells and protecting from immune system Bacteria and Archaea  DNA - some bacteria have a membrane around their nucleoid  Size - largest prokaryotes are the size of eukaryotes  Organization - Colonies, chains, biofilms (bacteria live in), but not truly multicellular (groups)  Organelles - lack formal organelles - compartmentalization does occur  diagram is wrong Epulopiscium fishelsoni  Guest at a fish’s banquet  600 μm in length  Most prokaryotes are smaller (1×2 μm)  Found in digestive system of sturgeon fish  Largest known prokaryote Thiomargarita namibiensis  Sulfur pearl of Namibia  Ocean sediments ** The largest bacterium to date - 750 μm in diameter  Visible to the naked eye - size of period in a textbook  in chains Thermodiscus maritimus  One of the smallest organisms - diameter of 0.2 μm  Archaea Nanobacteria  Diverse uncultivated ultra-small bacterial cells in groundwater  Can pass through 0.2 μm filter 3  Volume of E. coli ~1.0 μ  0.5 μ in width by 2.0 μ in length  Volume of ultra-small bacteria is 0.009 μ 3  150 of the ultra-small bacterial cells could fit into a single E. coli cell Biofilms  Microbial community - complex - like to live together, but can survive on own - several species  Physiologically integrated - dependent on each other  How bacteria and archaea live in nature - extracellular polysaccharide - protective and adhesive matrix - protected from the environment - protected from protozoan  eat bacteria - protected for phagocytic cells - protected from antibiotics and chemicals - promotes conjugation Cell-Cell Communication  Bacteria and archaea communicate with one another within biofilms - emit signal molecules protected by other organisms and the communication (chemical signals) create biofilms Quorum Sensing The ability of bacteria to communicate and coordinate behavior via signaling molecules - create biofilm A phenomenon in bacteria that limits certain behaviors to occurring only above a certain population density The process in which single-celled organisms, usually bacteria, monitor population density by detecting the concentration of small diffusible signal molecules Prokaryotes have a cytoskeleton  Bacteria and Archaea have homologs of the 3 major types of eukaryotic cytoskeletal proteins: - actin, tubulin, and intermediate filament proteins - genes for proteins  Bacteria also have a 4 type, the MinD-ParA group required for cell division - cytoskeleton for cell division  The prokaryotic cytoskeletal structures are involved in cell division, cell polarity, cell shape, and plasmid partition and chromosomes Bacteria have a lipid-based plasma/cell membrane  Make creative use of their membranes to accomplish many tasks Chloroplasts are absent in bacteria  In bacteria, photosynthetic pigments are integrated into internal membranes  Invagination of the plasma membranes  Chlorosomes - maximize membrane space with photosynthetic pigment  Specialized membranes associated with the plasma membrane  Exact same process as that occurs in chloroplasts ** no known photosynthetic Archaea Use of membranes  Generate ATP via an electron transport chain - same process that occurs in mitochondria Physiological diversities  Some use organic (C H O6) 12l6cules as sources of e s - Ex. sugar 2- 2+ -  Others use inorganic molecules (H , NO 2 Fe ) as a source of e s ** Catabolic processes to breakdown -  Aerobic organisms use O as f2nal e acceptor  Anaerobic organisms use something else as a final e acceptor: - SO 42- - carbonate - - NO -2-itrate - CO 3 - carbonate  Obligate aerobes - require O 2  Obligate anaerobes - avoid O 2  Facultative anaerobes - use O ,2but can survive anaerobically  Aerotolerant - tolerate, but not require O 2  Microaerophiles - survive in low [O ]2 Nitrogen (N ) f2xation  Life is not possible without bacterial N fi2ation  N2is inert - breathe in but don’t use  humans  N2is converted NH (am3onia) by bacteria - symbionts of plants  live on surface of root of inside of root - free living bacteria  not associated with plant; in soil  NH 3s building block for amino acids and the bases (A,T,G,C) in nucleotides Cell Wall  Exterior to the membrane - composed of carbohydrates and protein  Most but not all, bacteria have a cell wall  All Archaea have cell wall  The most common bacterial cell wall is made of peptidoglycan - a carbohydrate unique to bacteria  There are bacterial species that do not have a cell wall or have cell walls that are very different  Archaea have several unique types of cell walls  Net/mesh - around cell wall  Exterior to membrane  String of amino acids **Peptidoglycan  Carbohydrate  Macromolecule composed of a repeating framework of long chains cross-linked by short peptide fragments - unique to bacteria - composed of 2 sugars: NAG & NAM - sugars alternate in the backbone - rows linked by polypeptides  Provides strong, flexible support to keep bacteria from bursting or collapsing because of changes in osmotic pressure  Chains of NAG & NAM are connected by peptide bridges - peptides are short chains of amino acids  Peptidoglycan is unique to the bacteria and many antibiotics target this structure ** Penicillin blocks formation of a pentaglycine bridge Gram (+) & (-) **will be on exam (be able to identify parts) Gram (-)  Stain pink/red  Has 2 membranes - outer membrane - plasma membrane  lipopolysaccharides  thin peptidoglycan layer Gram (+)  Stain purple  One membrane  Thick peptidoglycan layers Endospores  Produced during times of stress/starvation by bacteria - thick-walled survival structure  Organism can exist in the spore state for 100s of years  Composed of peptidoglycan  Some spore formers are pathogens and additional antiseptic procedures are required for elimination Sporulation Cycle  Starvation state  Onset state  Commitment state  Engulfment state  Maturation state  Mother cell lysis  Germination  Vegetative state Genome  Greater than 2,000 prokaryotic genomes have been sequenced - genome is all the DNA and plasmids in a cell  Genome size varies tremendously - 490,000 bp (smallest) – 9,105, 828 bp (largest)  huge range ** bp  base pairs  Gene number varies - 480 (smallest) – 6,700 (largest) - E. coli has 4,500-5,000 genes  Tremendous  Smaller genomes associated with restricted environment  Obligate symbionts and near obligate parasites without a host in nature Ex. Buchnera aphidicola has 600 genes and cannot survive outside its aphid host  These organisms are missing genes and are dependent upon host for common components - lipids - amino acids - nucleotides - vitamins - enzymes for cell wall synthesis - citric acid cycle  Larger genomes are associated with species that live in highly complex and/or variable environments - free living Ex. Bradyrhizobium (9,105,828 bp), Streptomyces (8,677,507 bp), and Sorangium (13,033,779 bp)  Live in soil - genes needed to survive wet and dry environments Other Highlights  Some prokaryotes have more than 1 chromosome - diploid  Vibrio has 2 circular chromosomes  Borrelia has 1 linear chromosome and 21 smaller linear  Agrobacterium has 1 circular and 1 linear chromosome  No eukaryotes have circular and linear chromosomes Plasmids  Extra-chromosomal DNA in bacteria and archaea - mini chromosomes with genes  Plasmids contain ~10-100 genes  Cells contain 1-100 plasmids  Megaplasmids - 1/3 the size of the chromosome  Bacteria perform conjugation - pass back and forth plasmids


Buy Material

Are you sure you want to buy this material for

25 Karma

Buy Material

BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.


You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

Why people love StudySoup

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"

Anthony Lee UC Santa Barbara

"I bought an awesome study guide, which helped me get an A in my Math 34B class this quarter!"

Bentley McCaw University of Florida

"I was shooting for a perfect 4.0 GPA this semester. Having StudySoup as a study aid was critical to helping me achieve my goal...and I nailed it!"

Parker Thompson 500 Startups

"It's a great way for students to improve their educational experience and it seemed like a product that everybody wants, so all the people participating are winning."

Become an Elite Notetaker and start selling your notes online!

Refund Policy


All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.