microbe mission 2 Flashcards
What is the structure of bacteria?
Unicellular organisms with a simple structure.
What is the bacterial membrane composed of?
- Phospholipid bilayer
- Proteins
- Lipopolysaccharides (in gram-negative bacteria)
What is the function of the bacterial cell wall?
Provides structural support and protection, maintains cell shape, and prevents osmotic lysis.
What are bacterial flagella used for?
Enable bacterial motility through rotation.
What are bacterial pili (plus) used for?
- Genetic material transfer (conjugation)
- Attachment to surfaces or each other
What are bacterial fimbriae?
Short hair-like structures used to attach to surfaces or host tissues.
What is the bacterial nucleoid?
Region within cytoplasm containing DNA.
What is the bacterial cytoplasm composed of?
- Water
- Enzymes
- Ions
- Small molecules
- Ribosomes
What are bacterial gas vesicles used for?
Provide buoyancy to allow aquatic bacteria to float at specific depths.
What are endospores?
Highly resistant, dormant forms of bacteria encased in a tough coat.
What are archaea?
Microorganisms similar to bacteria but capable of surviving in extreme environments.
What is unique about the archaeal cell membrane?
Contains ether linkages and can be lipid monolayers or bilayers.
What is the archaeal cell wall composed of?
- Pseudopeptidoglycan
- Polysaccharides
- Proteins
What are eukaryotic cells characterized by?
More complex structure with membrane-bound organelles.
What is the eukaryotic cell membrane composed of?
- Lipid bilayer
- Embedded proteins
- Cholesterol
What are the organelles of the eukaryotic cell?
- Mitochondria
- Endoplasmic reticulum
- Golgi apparatus
- Lysosomes
What is the function of contractile vacuoles?
Maintain osmotic balance in some protists.
What are eyespots used for in some protists?
Detect light to help the organism orient itself.
What are carboxysomes?
Protein shells containing enzymes for carbon fixation.
What is the structure of gram-positive bacteria?
Thick peptidoglycan layer with teichoic acids, no outer membrane.
How do gram-negative bacteria differ from gram-positive bacteria?
Thin peptidoglycan layer with an outer membrane made of lipopolysaccharides.
What characterizes acid-fast bacteria?
Cell wall made of mycolic acids, appears red/pink after staining.
What is the gram stain procedure?
Distinguishes between gram-positive and gram-negative bacteria.
What is a virus?
Unique microorganisms capable of infecting host organisms.
What does a viral genome consist of?
Either DNA or RNA, can be single or double stranded.
What is a capsid?
Protein shell that surrounds and protects the viral genome.
What is an envelope in the context of viruses?
A lipid bilayer from the host cell that surrounds some viruses.
What are spike proteins/glycoproteins?
Glycoproteins that recognize and bind to host cell receptors.
What role do enzymes play in some viruses?
Contribute to replication in the host cell.
What is a lipid culture/broth culture?
Bacterial culture method using nutrient-rich liquid medium.
What is an agar culture/solid culture?
Bacterial culture method using gelatinous agar to isolate colonies.
What is the plate count method?
A method for counting living bacterial cells by diluting and counting colonies on agar plates.
How is optical density measured in bacterial cultures?
By measuring the cloudiness or turbidity of the culture using a spectrophotometer.
What are the types of chemical sterilization?
- Alcohols
- Aldehydes
- Halogens
- Hydrogen peroxide
- Phenolics.
What are limitations of culture-based approaches to study microbes?
Microbes may require specific conditions to culture, behave differently in isolation, and may not reflect natural communities.
What is binary fission?
Asexual bacterial cell division.
What happens during the initiation phase of transcription?
RNA polymerase binds to the promoter, forming a transcription bubble.
What occurs during the elongation phase of transcription?
RNA polymerase adds ribonucleotides complementary to the DNA template.
Describe termination in transcription.
RNA polymerase encounters a terminator sequence, releasing the RNA.
What is the endosymbiotic theory?
Proposes that mitochondria and chloroplasts evolved from prokaryotic ancestors.
What are some adaptations of microbes to extreme environments?
- Accumulation of sugars and amino acids
- Changing lipid bilayer composition
- Resistant spores or extremozymes.
swimming motility
involves flagella, which can be monotrichous (single flagellum at one end), lophotrichous (multiple flagella at one end), amphitrichous (flagella at both ends), or peritrichous (flagella distributed over surface). Flagella rotate in propeller-like motion. Examples: E. coli, P. aeruginosa
gliding motility
involves secretion of slimy extracellular matrix or surface proteins. Includes twitching, where pili extend and attach and retract, or slime excretion, where mucus-like substances are exceted for sliding across surfaces. Examples: M. xanthus, cyanobacteria
chemotaxis
cells move toward or away from chemical stimuli like nutrients or toxins. Signaling involves detection of chemical gradient by receptors which affect flagella rotation to steer the cell
phototaxis
cells move toward or away from light sources. Photoreceptors sense light and cell’s motility apparatus is modulated accordingly. Examples: purple sulfur bacteria, chalmyomonas
plasmids
small circular dsDNA molecules that exist independently of bacterial chromosome, often found in bacteria. Smaller than chromosomal DNA, replicate independently of bacterial chromosome, transferable between bacteria through processes like conjugation. Can carry genes for antibiotic resistance, encode proteins to kill other bacteria, carry genes to enable pathogenic bacteria to cause disease. Can help bacteria survive in hosts that have antibiotics, help bacteria metabolize unusual substances, help disease spread, and enable rapid acquisition of new genetic traits
recombinant dna technology
combining DNA from different organisms to create new genetic combinations. Gene encoding useful protein is isolated from source organism, inserted into a plasmid vector, introduced into a bacterial cell, cultured to express the gene, and harvested for medical use. Example: insulin from animal pancreases can be produced for humans by inserting gene into plasmid vector, introducing into E. coli bacteria, and producing insulin when bacteria multiply.
electron donors and acceptors
substances that donate or accept electrons to produce energy in the form of ATP
alternative electron donors
glucose, organic acids, aminoacids, hydrogen, sulfur compounds, ferrous iron, manganese
alternative electron acceptors
oxygen, nitrate, sulfate, carbon dioxide, fumarate, metal ions
Winogradsky column
model system used to study microbial diversity and biogeochemical cycles in natural environments by simulating oxgygen, light, and nutrients. Microbial communities in the column carry out processes like photosynthesis, sulfur reduction, and carbon fixation
what do nutrient media contain typically
carbon source like glucose, nitrogen source like peptones or ammonium salts, minerals like potassium/magnesium, vitamins/growth factors like biotin or thiamine, and agar or liquid components to create a solid media or broth
great plate count anomaly
indicates that the number of colony-forming units (CFUs) counted on agar plates is often much lower than the number of viable cells in a sample, likely due to microorganisms being viable but not culturable.
gram stain procedure
distinguishes between gram-positive and gram-negative bacteria. done by applying crystal violet stain, applying iodine solution (mordant) that binds to violet dye, then wash smear with alcohol or acetone to see if the cells remain violet or are colorless. counterstains such as safranin stain decolorized cells, causing gram-negative cells to appear red or pink and gram-positive cells to remain violet
