Microbiology Flashcards
Differences between archeal and bacterial phospholipids
Archea
- Have phytanyl side chains
- Contain ether linkages (C-O)
- Contain L-glycerol
Bacteria
- Unbranched side chains
- Contain ester linkages (O=C-O)
- Contain D-glycerol
Describe the external structures unique to prokaryotes
Glycocalix
- Slime layer made up of glycoprotein that allows the bacteria to adhere to their environment
Capsules
- Thick polysaccharide layer that prevents phagocytosis (Gram -ve only)
Pili and Fimbriae
- Allow for adherence to the host in pathogenic/parasitic relationships
Flagella
- Hollow tubules made of flagellin used for locomotion
Define Binary Fission
Binary fission is when a bacterium splits into two equally sized daughter cells, each containing a copy of the mother cells genetic material
Describe the stages of the bacterial cell cycle
B/G1 = Cell growth phase (time taken varies) C = Chromosome replication (40mins) D = Septum formation + cell division (20mins)
Why does cell division time in bacteria vary?
Some bacteria can have a division time of <60 mins due to them starting another round of chromosome replication immediately before cell division. This means that the daughter cells acquire a chromosome that is already halfway through replication, speeding up the time taken to replicate rest of the chromosome.
Name 2 methods of measuring bacterial growth
Spectrophotometry (measuring the optical density)
Dilution + plate count
What makes a pathogen?
A microorganism that is able to cause disease in an animal, plant or insect. A pathogen shows both Invasiveness and Toxicity.
Name 4 routes of transmission of bacteria
- ) Inhalation of contaminated air –> Respiratory diseases
- ) Ingestion of contaminated food/water –> intestinal diseases
- ) Contact with another infected host –> STDs
- ) Bites from an infected organism –> vector-borne diseases
Name the methods underpinning invasiveness
- Colonisation
- Production of extracellular substances which facilitate invasion (invasins)
- Evasion of host defenses
Name the methods underpinning toxicity
- Causing damage to the host by producing Exotoxins
- Destruction of cellular structures
- Can also produce Cytotoxins, Endotoxins and Neurotoxins
How do antibiotics work?
They interfere with a bacteria-specific biological process, such as;
- cell wall synthesis
- cell membrane structure
- protein synthesis
- nucleic acid synthesis
How do you define fungi?
Fungi are microorganisms that do not contain chlorophyll and have a rigid cell wall made of chitin or cellulose
Name 2 microscopic and 2 macroscopic features of fungi
Micro
- Chitin cell walls
- Spore production
Macro
- Fruiting bodies
- Hyphae
Describe how fungi obtain nutrition
Fungi assimilate a wide range of organic compounds and produce a wide range of secondary metabolites.
Fungi are responsible for decay and recycling of organic material as they are saprophytes.
They can also break down recalcitrant macromolecules like cellulose, keratin and lignin.
Discuss fungal infection in humans
Most fungi are harmless to humans and tend to be opportunistic pathogens, so they typically infect those who are immunocompromised.
Only about 50 species are known to cause human
disease, serious infection tends to be rare, but superficial
infection is common
Fungal infection in more common in plants
Discuss fungal infection in plants
Fungi affect plants by
- Producing degenerative enzymes
- Destruction of plant growth regulators
- Production of toxins that interfere with cell membranes + mitochondria
- Altering metabolic activities of the plant
- Blocking water transport and transpiration
Discuss methods of controlling fungal infections
Antibiotics exploit differences between eukaryotic and prokaryotic cells, however, control is difficult as fungi develop resistance to anti-fungal agents and the host is likely to suffer from side effects
Define Archea
Archea are prokayotic, unicellular organisms that inhabit ecological niches
List the problems associated with thermophiles surviving at high temperature
- Denaturation of biomolecules – Particularly protein and nucleic acids
- Membrane fluidity – membranes become more fluid
- Solubility of gasses in liquids – decease in gas concentration proportional to temperature and pressure
List the adaptions of thermophiles that allow them to survive at high temperatures
- Phospholipid monolayer
- Membranes can contain C rings
- More thermostable proteins
- Increased K+ levels protect DNA
List the adaptions of psycrophiles that allow them to survive at low temperatures
- Cell membranes contain unsaturated lipids
- Use of anti-freeze proteins
Define gene transfer
Gene transfer is the movement of genetic material. This can be horizontal (between organisms) or vertical (between generations.) eg./ photosynthesis was transferred between algae and euglena
Define endosymbiosis in relation to gene transfer
Endosymbiosis is the process by which one cell engulfs another, this can also lead to horizontal gene transfer
This can be seen in Mitochondria and Chloroplasts:
• Contain DNA
• Contain own ribosomes
• Sensitive to antibiotics
• Sequencing data demonstrates gene transfer
• Eukaryotic nucleus contains bacterial genes
What are the basic features and functions of viruses?
Features
- Nucleic acids surrounded by protein coat
- Replication is dependent on host cell
- Intracellular and extracellular phases
Functions
- Introduced into population
- Spread + infect other members
- Escape the bodies defenses
- Cause disease
Name the 4 categories of virus
- ) Retrovirus
- ) Single-stranded RNA (+ and - sense)
- ) Double stranded RNA virus
- ) Double stranded DNA virus
Describe how a Retrovirus infects a cell
- ) Entry
- ) Viral reverse transcriptase converts one RNA strand into ssDNA and the dsDNA
- ) dsDNA reaches the nucleus
- ) Viral integrase incorporates dsDNA into host DNA
- ) Transcription and translation of viral DNA
- ) Proteins produced to produce new virion casings
- ) Virions encapsulated and released
Describe how a -ve sense ssRNA virus infects a cell
- ) Entry
- ) -RNA strand converted to +RNA strand via viral RNA polymerase in nucleus
- ) RNA replication
- ) mRNA translated to produce viral proteins
- ) Virions produced
Describe how a +ve sense ssRNA strand infects a cell
- ) Entry
- ) RNA is translated in cytoplasm
- ) Genome is replicated
- ) Viral proteins used to produce new virions
- ) Virions bud from cell
Describe how a dsDNA virus infects a cell
- ) Entry
- ) Viral DNA transported to nuclues
- ) Host RNA polymerase converts Viral DNA to mRNA
- ) Viral mRNA translated, protein transported back to nucleus
- ) Viral DNA replicated
- ) Viral DNA and proteins re-assemble and released
Describe how a dsRNA virus infects a cell
1.) Entry
2.) Proteins in virus develop into inner core
3.) 10 mRNA gene segments inserted into core
4.) -RNA strand is copied on viral mRNA to replicate genome
5.) Inner core used for:
• mRNA transcription
• Virion progeny production
Describe the life cycle of a lytic bacteriophage
- Attachment
- Penetration
- Transcription
- Replication of phage DNA, Synthesis of proteins
- Assembly
- Release
Describe the Life cycle – temperate bateriophage
- Attachment
- Linear phage DNA circularizes
- Replication (lytic) or 3. Integration (lysogenic)
• Excision/Replication - New virions formed
- Cell lyses releasing phage virions
Explain the biology of smallpox and why it is now extinct
Smallpox was a wide spread disease spread by person-to-person contact. It had a 20-30% mortality rate.
The virus was eliminated via a successful vaccination program, smallpox was a good target for this as;
- It was exclusive to humans
- It had easy to spot symptoms allowing for easy quarantining of carriers
- Only one serotype
- Vaccine was 100% successful
Pros and cons of an attenuated Polio vaccine
Pros • Effective • Lifelong immunity • Induces immune (antibody) response similar to natural infection • Indirect community immunization through spread of the attenuated virus • Administration (oral) • Booster vaccines not required
Cons
• Vaccine-induced (iatrogenic) poliomyelitis
• Spread to contacts without consent
• Unsafe for immunodeficient individuals
Pros and Cons of an inactivated Polio vaccine
Pros
• Can be incorporated into routine immunizations with DPT
• Good stability in transport and storage
• No risk for poliomyelitis in recipients and contacts
• Safe for immunodeficient individuals
Cons • Does not induce local (gut) immunity • Booster vaccines required • Administered as injection • Higher community vaccination levels required
Name the two important proteins of the coat of an influenza virus and their functions
Hemagglutinin (HA) - Attaches to host receptors
Neurminidase (NA) - Breaks down sialic acid to allow budding
What is the difference between antigenic shift and antigenic drift
Antigenic drift - Minor mutations occurring regularly (eg./ seasonal flu)
Antigenic drift - Recombinance between flu strains that infect different species leading to re-assortment of the genome (eg./ Spanish flu)
Ways that microbes obtain C and energy?
C - Photosynthesis/organic material
Energy - Respiration/fermentation
Name some of the Biogeochemical cycles that microbes play a key role in
Carbon cycle
Nitrogen cycle
Sulphur cycle
Iron cycle
Name some positive interactions between microbes and other organisms
Mycorhizzae - between plant roots and fungi Lychens - Fungi and algae Rumminants Leaf cutter ants Gut microbiota
Name methods of removing products from a fermentor
Common methods include: • Distillation, • Precipitation & Flocculation • Centrifugation • Filtration, • Solvent Extraction • Chromatography
Define Algae
Eukaryotic microorganisms that contain cholorplasts and can perform photosynthesis, they can be both macro and microscopic
