Week 6 (Part 1): Bacteria Flashcards
T/F
Bacteria are unicellular, prokaryotic cells that have no true nucleus
True
What is found in the surface layer of bacterial cells? (3)
- Capsule:Found in some bacterial cells, this additional outer covering protects the cell when it is engulfed by other organisms, assists in retaining moisture, and helps the cell adhere to surfaces and nutrients.
- Cell Wall:Thecell wallis an outer covering that protects the bacterial cell and gives it shape. It acts as another layer of protection from the outside environment and controls permeability and prevents dehydration. Provides platform surface platform for appendages such as flagella and pili.
- Plasma Membrane:Thin wall that separates the cell wall from the cytoplasm. Acts as a semipermeable membrane: control the inflow and outflow of metabolites
What are other structures found in the bacterial cell? (4)
- Cytoplasm:Cytoplasm is a gel-like substance composed mainly of water that also contains enzymes, salts, cell components, and various organic molecules. It also contains the nucleoid, and ribosomes
- Ribosomes:Ribosomesare cell structures responsible forproteinproduction.
- Plasmids:Plasmids aregene-carrying, circular DNA structures that are not involved in reproduction.
- Nucleoid Region:Area of the cytoplasm that contains the single bacterial DNA molecule.
Name 2 bacterial appendages:
- Pili(Pilus singular):Hair-like structures on the surface of the cell that attach to other bacterial cells. Shorter pili called fimbriae help bacteria attach to surfaces.
- Flagella:Flagellaare long, whip-like protrusions that aid in cellular locomotion.
We talked about these two things in our first week, when we discussed virulence factors
T/F
Bacteria contains only DNA, not RNA
False
They contain both DNA and RNA
Morphology (shape):
Describe cocci bacteria (5).
The cocci are spherical or oval bacteria having one of several distinct arrangements:
- Biplococcus: cocci arranged in pairs
- Streptococcus: cocci arranged in chains
- Tetrad: cocci arranged in squares of 4
- Sarcina: cocci in arranged cubes of 8
- Staphylococcus: cocci arranged in irregular, often grape-like clusters
Morphology (shape):
Describe bacilli bacteria (3).
Bacilli are rod-shaped bacteria:
- bacillus: single bacilli
- streptobacillus: bacilli arranged in chains
- coccobacillus: oval and similar to a coccus
Morphology (shape):
Describe spiral bacteria (3).
Spirals come in one of threeforms:
- vibrio: a curved or comma-shaped rod
- spirillum: a thick, rigid spiral
- spirochete: a thin, flexible spiral
T/F
Most prokaryotes reproduce asexually through a process called binary fission.
True
T/F
During binary fission, the single DNA molecule replicates and the original cell is divided into two identical cells.
True
Describe the steps of Binary Fission:
- Binary fission begins with DNA replicationof the single DNA molecule. Both copies of DNA attach to the cell membrane.
- Next, the cell membrane begins to grow between the two DNA molecules. Once the bacterium just about doubles its original size, the cell membrane begins to pinch inward.
- A cell wall then forms between the two DNA molecules dividing the original cell into two identicaldaughter cells. However this mode of reproduction does not producegenetic variationwithin the organism. Genetic variation within prokaryotic organisms is accomplished throughrecombination.
- In recombination, genes from one prokaryote are incorporated into the genome of another prokaryote. Recombination is accomplished inbacterial reproductionby the processes of conjugation, transformation, or transduction.
What is fission?
Fission is the act of cleaving or splitting into parts.
Describe conjugation, transformation, and transduction:
- Conjugation: bacteria connect through a protein tube structure called a pilus.
- Genes are transferred between bacteria through the pilus.
- Conjugationinvolves transfer of DNA via sexual pilus and requires cell –to-cell contact. - Transformation: bacteria take up DNA from their surrounding environment.
- The DNA is transported across the bacterial cell membrane and incorporated into the bacterial cell’s DNA. - Transduction: the exchange of bacterial DNA through viral infection.
- Bacteriophages, viruses that infectbacteria, transfer bacterial DNA from previously infected bacteria to any additional bacteria that they infect.
- Transductioninvolves transfer of DNA from one bacterium into another via bacteriophages.
- DNA fragments that contain resistance genes from resistant donors can then make previously susceptible bacteria express resistance as coded by these newly acquired resistance genes.
How is the chemical nature of the bacterial cell wall divided?
Into 2 groups:
1) Gram positive
2) Gram negative
How many layers do gram-positive and gram-negative bacteria have?
- What is present in both?
- Explain any differences.
Both gram-positive and gram-negative organisms have more than 1 layer protecting their cytoplasm, and nucleus from the extracellular environment.
- The layer just outside the bacterial cytoplasmic membrane is the peptidoglycan layer or cell wall it is present in both gram-positive and gram-negative organisms
Difference:
- In gram +ve bacteria this peptidoglycan wall is thick
- In gram –ve bacteria it is very thin
