Exam 1 Chapter 22 Prokaryotes Flashcards
Microbiome
The full array of microorganisms (the microbiota) that live on and in humans and, more specifically, the collection of microbial genomes that contribute to the broader genetic portrait, or metagenome, of a human. The genomes that constitute the human microbiome represent a remarkably diverse array of microorganisms that includes bacteria, archaea, fungi, and even some protozoans and nonliving viruses. Bacteria are by far the most numerous members of the human microbiome: the bacterial population alone is estimated at between 75 trillion and 200 trillion individual organisms, while the entire human body consists of about 50 trillion to 100 trillion somatic (body) cells
prokaryote modern classification
based on sequencing of proteins, DNA, and RNA
prokaryote facts
1) oldest organisms on Earth with fossils ~3.5 billion years old
2) structurally simplest organisms
3) most abundant life forms on earth
4) 90-99% unknown and undescribed.
5) lack a membrane bound nucleus and other organelles or cell inclusions.
6) Lack of cell compartments.
7) Include 2 domains Bacteria and Archaea.
Consider: Archaea and Eukarya share nucleic acid similarities so Eukarya split off from Archaea
cyanobacteria
group of bacteria that produced oxygen and changed the Earth’s atmosphere from an anoxic one to one rich in oxygen.
Can photosynthesize
Prokaryote vs Eukaryotes
Eukaryotes have organelles, nucleus. Both have ribosomes. (see more for this)
Bacteria vs Archaea
- cell wall composition
- plasma membrane make-up
- DNA replication
- gene expression
- Bacteria have peptidoglycan which Archae lack.
Consider: Archaea are able to live in the most extreme environments.
prokaryote structure (bacteria)
have cell walls consisting of a network of polysaccharides connected by cross links of polypeptides (peptidoglycan)
flagella - used for movement
have enzymes used for cellular respiration attached to cell membrane
have 3 shapes (due to cell walls): bacillus, coccus, and spirillum
can form biofilms
exchange of genetic material via horizontal transfer
occurs through conjugation (depends on presence of conjugative plasmids when genes are transferred through rigid, tubular sex pili), transduction (occurs when viruses (bacteriophage) package host DNA and transfer it upon subsequent infection), transformation (bacterial cells pick up free pieces of DNA from the medium-pieces that were released from dead bacteria), and exchange of R plasmids (plasmids are different from bacterial chromosomes in that plasmids have few genes, bacterial chromosome have many)
increases genetic diversity; helps infer phylogeny; common occurrence in bacteria; can produce large genetic change
conjugation
- exchange of genetic material via horizontal transfer
- depends on presence of conjugative plasmids when genes are transferred through rigid, tubular sex pili
transduction
- exchange of genetic material via horizontal transfer
- occurs when viruses (bacteriophage) package host DNA and transfer it upon subsequent infection
transformation
exchange of genetic material via horizontal transfer
bacteria cells pick up free pieces of DNA from medium pieces that were released from dead bacteria
R plasmids
have fewer genes than bacterial chromosomes
gram positive
positive bacteria have thick peptidoglycan wall with small amounts of teichoic and lipoteichoic acid.
will stain PURPLE color
gram negative
contain lipopolysaccharides, less peptidoglycan and no acids and do not retain purple colored dye.
lipopolysaccharides
more resistance to penicillin
E. coli
found in the lower intestine of warm blooded animals; 5000 genes, help host by producing vitamin K2
Consider: TB, cavities and several STDs caused by bacteria.
endospores
thick-walled structures that contain chromosome and small amount of cytoplasm…these are formed in response to environmental stress (e.g., low nutrients)
Beneficial bacteria
Decomposers play an important role in the environment. Decomposition differences between a fish caught in Canada and Florida when put on ice???
Rhizobium
example of a diazotrophs (nitrogen fixing bacteria)…only organisms (bacteria group) capable of taking gaseous nitrogen and combining it with hydrogen to make ammonia
MAKES AMMONIA
diazotroph
nitrogen fixing bacteria
nitrogen fixation and use
this pathway begins with atmospheric nitrogen ( Dinitrogen; unusable by plants in this form because of strength of N-N triple bond), bacterial nitrogenase(enzyme that catalyzes the reactions); ammonia; conversion by plants or algae; synthesis of proteins
binary fission
reproductive process that produces identical cells by simple splitting
symbiosis
Types of symbiotic relationship and influence on evolution. (Mutualism, Commensalism and Parasitism)
nucleoid region
area where prokaryotic DNA is found (no membrane)
