Basic Bacteriology Flashcards
What are the characteristics of Bacteria?
- Simple unicellular prokaryotes
- Prokaryotes lack membrane-enclosed organelles
What is a bacteria’s cell wall made from?
Peptidoglycan
How do bacteria reproduce?
Binary fission
What is the process of Binary Fission?
- Cell replicates its DNA
- The cytoplasmic membrane elongates, separating DNA molecules
- Cross wall forms; membrane invaginates
- Cross wall forms completely
- Daughter cells
What are the Characteristics of Fungi and how do they reproduce?
- Diverse group of organisms; molds, mushrooms, yeasts
- Reproduce asexually or sexually
What are the characteristics of Protozoa?
- Single-celled eukaryotes
- Diverse group of organisms:
- Vary in size, shape, features and habit
What are the characteristics of Viruses and how do the reproduce?
- Acellular
- have DNA or RNA core, surrounded by a protein coat
- coat may be enclosed in an envelope
- have DNA or RNA core, surrounded by a protein coat
- Only seen with electron microscope
- Reproduce only in host cell by using its cellular machinery
What are the differences between Prokaryotic Cells and Eukaryotic Cells?
-
Prokaryotic Cells
- Smaller, um
- No true nuclear membrane
- Haploid
- Circular DNA
- Can exist independently in nature or in many environments
- Ubiquitous in nature
- Asexual
-
Eukaryotic Cells
- Larger
- True nucleus
- Membrane enclosed organelles
- Linear DNA
- Diploid
- Can reproduce sexually
- Increased genetic diversity
Compare Gram Positive and Gram Negative Bacteria
-
Gram Positive
- Thick cell wall
- Inner membrane
- Break cell wall, immediate cell death
-
Gram Negative
-
Double membrane
- Thin cell wall, inner and outer membrane
-
Double membrane
What are the characteristics of Spores?
- Thick-walled, differentiated structure
- Highly heat, radiation, chemical and dessication resistant
- Commonly isolated from soil
- Bacteria can endure nutrient depletion, harsh conditions and facilitate dispersal in the enviornment, wind, water and animal GIT
What is glycolax?
A substance that surround bacterial cells
- Capsule: if organised and firmly attached to cell wall
- Slime layer: if unorganised and loosely attached to cell wall
Describe the characteristics of the Capsule
- Dense, well-defined polysaccharide or protein layer closely surrounding a cell
- More resistant to physical and chemical agents and antibiotics
- Facilitate adherence to host cells and surfaces (biofilms)
What are the characteristics of Flagella?
- Long, thin cellular appendage, capable of rotation in prokaryote cells and responsible for swimming motility
What are the characteristics of Exotoxins?
- Proteins produced more commonly inside gram-positive bacteria, as part of their own growth and metabolism
- Exotoxins are then secreted or released into the surrounding medium following lysis
What is one of the most potent endotoxin known?
Clostridium Botulinum
What are the Characteristics of Clostridium Botulinum and what symptoms do they produce?
- Gram positive rod; anaerobic
- Form heat resistant spores
- Produce very potent neurotoxins
- Symptoms:
- Initial: Nausea, vomiting, cramps, diarrhoea
- Neurological symptoms: Flaccid paralysis, death
What are the clinical applications of botulinum toxin?
- Botox treatment
- Therapeutic agent
- Blepharospasm
- Muscle spasms
- Migraine headaches
- Excessive underarm sweating
What are the Characteristics of Endotoxins?
What symptoms does it cause?
- Lipid portions of lipopolysaccharides (LPSs) that are part of the outer membrane of the cell wall of gram-negative bacteria
- The endotoxins are liberated when the bacteria die and the cell wall breaks apart
- Causes fever, low blood pressure, inflammation
- Responsible for dramatic effect of Neisseria meningitidis
What are the phases of the bacterial growth curve?
- A: Bacteria gets used to environment
- B: Amount of bacteria increases exponentially
- C: Amount of bacteria generated similar to the amount that die
- D: Death
What are the Factors Influencing Bacterial Growth?
- Temperature
- pH
- Water availability and osmotic pressure
- Oxygen availability
Describe the inflence of temperature on bacterial growth
- Minimum: Membrane gelling; transport processes so slow that growth cannot occur
- Maximum: Protein denaturation; collapse of the cytoplasmic membrane; thermal lysis
What is the optimum pH for bacterial growth?
- 7.2-7.6
What is an extremophile?
- An organism that grows optimally under one or more enviornmental extremes
What is a culture medium?
- Aqueous solution of various nutrients suitable for the growth of microorganisms
What are the nutritional requirements for the laboratory culture of microbes?
- Macronutrients: carbon source, nitrogen, potassium, sulphur e.t.c
- Micronutrients: trace elements e.g. boron, chromium, iron e.t.c
What culture media are used in laboratory culture of microbes?
- Liquid
- Solid: gelling agent usually agar added
Describe Chemically Defined Culture
- Exact chemical composition known
- General Purpose Complex: nutrient/blood agar e.t.c
Describe Differential Culture
- Contains indicators such as pH indicators or chromogens to identify target organism
Describe Selective Culture
- Combination of chemicals and antibiotics to select target bacteria
- Suppresses normal flora or contaminating bacteria
Describe Selective and Differential Culture
- MacConkey Agar (Mac)
What are the Steps when Culturing Bacteria?
- Inoculation
- Incubation
- Isolation
- Inspection
- Identification
Describe the Process of Inoculation
- Producing a culture
- Introduce a tiny sample (the inoculum) into a container of nutrient medium
What is the purpose of Culturing Bacteria?
- Used to manipulate, grow, examine and characterise microorganisms in the lab
Describe the Process of Incubation
What are the Types of Culture?
- An inoculated sample is placed in an incubator to encourage growth at optimal temperature
- 18°C-37°C
- Can control atmospheric gases e.g. CO2
- Can recognise growth as turbiditiy in liquid media and colonies on solid media
- Type of culture:
- Pure culture: growth of only a single known species (also called axenic)
- Mixed culture: two or more species
- Contaminated culture: includes unwanted microorganisms of uncertain identity or contaminants
What is the process of Isolation?
- Separating one species from another
What are the Steps involved in Inspection and Identification?
a. Appearance
b. Metabolism - biochemical tests
c. Genetic analysis - PCR
d. Protein Profile - mass spectrometry
Describe Appearance in Inspection and Identification
- Microscopy
- Observe unstained wet mount of bacteria
- Determine size and shape of bacteria
- Motility
- Stained preparations
- Bacteria fixed to slide by heat or alcohol
- Differential stain used:
- Gram Stain: +ve or -ve
- Add fast stain: to check for acid fast bacteria
- Spore stains, flagella stains, capsule stains
- Observe unstained wet mount of bacteria
Describe Metabolism in Inspection and Identification
- Biochemical tests
- e.g. nitrate broth, catalase
Describe Genetic analysis in Inspection and Identification
- PCR
- PCR to distinguish MRSA from MSSA
- Separate DNA and Stain
Describe Protein Profile in Inspection and Identification
- Mass spectrometry
- Separates proteins on their size; give proteins at peaks
- Can’t tell you if resistant or not
