Intro To Microbiology And Bacterial Structures (w19) Flashcards
What is a microorganism ?
Microorganisms (or microbes) are organisms that are too small to be seen with the unaided eye, require a microscope (except for some moulds)
What are the 5 major groups of microbes ?
1) Bacteria —> Bacteriology
2) Fungi (yeasts and moulds) —> Mycology
3) Parasites (protozoa, helminths, and ectoparasites) - Parasitology
4) Microalgae —> Phycology
5) Viruses and prions —> Virology
What id the general size order for microorganism diversity ?
- largest —> smallest
Moulds > Protozoa > Yeasts > Bacteria > Viruses > Prions
What does it mean when an microorganism is acellular ?
Acellular - without a cellular structure (e.g. viruses and prions)
What are the two types of classification of microorganisms ?
- cellular
- acellular
What are the three different types of domain ?
- bacteria
- archaea
- eakarya
When was the system for classifying biological organisms introduced ?
In 1990
What is classification mainly based on ?
Classification mainly based on differences in the sequences of nucleotides of ribosomal RNAs (rRNA)
What are the main features of bacteria/ archea ?
- the study is bacteriology
- are prokaryotes
- mostly unicellular/ monocellular
What are the main features of fungi ?
- study of fungi is called mycology
- are eukaryotes
- yeasts are unicellular
- mounds are pluricellular
What are main features of parasites ?
- study of parasites is parasitology
- are eukaryotes
- Protozoa are unicellular
- helminths are pluricellular
What are features of microalgae ?
- study of microalgae is phycology
- mostly eukaryotic
- both unicellular and pluricellular
What are the features of a virus ?
- study of virus is virology
- are acellular (no cellular structure)
- small infectious particles which consist of nucleic acid surrounded b a protective coat of proteins.
-coat may be enclosed in lipid envelope - don’t divide
- need to infect cell to replicate particles.
What are features of prions ?
- study of prions is virology
- Simpler infectious particles made up of only proteins - no nucleic acids
How are microorganisms essential for life on earth ?
- organic waste decomposition
- nitrogen fixation
- oxygen generation (photosynthesis)
- digestion and molecule generation
- production of food
- drugs/enzymes synthesis
How can bacteria be helpful ?
prevent growth of pathogens
produce growth factors (e.g. vitamins B and K)
breaking down toxic molecules, boosting the immune system and antimicrobial chemicals
What are the 4 types of arrangement of bacteria ?
- pairs (diplococci, diplobacilli)
- clusters (random planes - staphylococci)
- chains (one plane - streptococci, streptobacilli)
- groups of four (tetrads)
What is binomial nomenclature ?
Scientific names that’s are given to species of living things
What are bacteria and archea ?
- prokaryotes
- no nucleus
- without membrane-bio uni organelles and have simple organisation.
List function of plasma membrane ?
- serves as a selectively permeable barrier
- controls movements of molecules across the cells
- has infoldings called mesosomes, they are the site for DNA replication and cellular respiration.
What is the name given to the sterol-like molecules found in the plasma membrane ?
Hopanoids
List functions of cell wall …
- Maintain bacterial cell integrity and shape
- Prevents the cell from bursting when water flows into the cell by osmosis
- Can contribute to pathogenicity (ability to cause disease)
What is the evidence for the importance of the cell wall …
- Only a few bacteria do not posses cell walls (e.g. mycoplasma)
- Target of many antibiotics (anti-bacterial drugs)
What is a peptidoglycan ?
An essential component of the bacterial cell wall
What is the composition of the peptidoglycan (Murein) ?
- A rigid multi-layered network made up of linear chains
- Each chain is a polymer of a repeating identical disaccharide unit (made up of the following 2 monosaccharides) in long rows:
-N-acetylglucosamine (NAG)
-N-acetylmuramic acid (NAM) - A tetrapeptide chain of 4/5 amino acids is linked to NAM
- Chains are linked by peptide cross bridges between tetrapeptide side chains of NAMs
What do repetitions of peptidoglycan subunits form ?
Individual strands or chains
What are bacterial transpeptidase responsible for ?
(Penicillin-binding proteins) are responsible for these links (peptide cross link bridges) and are the target of beta-lactams e.g. pencillins
What do Beta-lactam antibiotics (including penicillins and other classes) to do peptidoglycan synthesis ?
Inhibits the peptidoglycan synthesis of the bacterial cell wall
What is the structure or Gram +ve ?
- Consists of a thick structure (several layers) of peptidoglycan, separated from the plasma membrane by a thin periplasmic space
- Also contains teichoic acids, made up of an alcohol and a phosphate group (negative charge)
-Bind to and regulate movement of cations into cell
-Regulate cell growth and prevent cell lysis
-Linked also to the cell membrane
What is the structure of Gram -ve ?
- Cell wall is thinner, more complex and more susceptible to mechanical breakage
Consists of:
-a thin peptidoglycan layer
-periplasmic space, containing degradative enzymes and lipoproteins
-outer membrane (the most external)
What is the functions of the outer membrane in Gram-bacteria ?
- Evade phagocytosis and immune system
- Permeability barrier to antibiotics (penicillin), digestive enzymes, etc
What is the main difference between gram-positive and gram-negative cell walls ?
Gram positive :
- thick peptidoglycan
- teichoic acids
Gram negative:
- Thin petidoglycan
- Has an outer membrane (containing LPS,Lipoproteins and porins)
- have periplasmic space
What is gram-staining used for ?
- To distinguish groups between bacteria according to their cell wall structure.
- also for better visual observation to highlight difference Rickey components in bacteria.
List the process of gram staining ;
1) fixation
2) primary staining
3) mordant application
4) decolourisation
5) counterstaining
What are the functions of the glycocalix ?
- Confer pathogenicity (only capsule)
- Prevent phagocytosis by host phagocytes
- Avoid desiccation by preventing water loss
- Aid in attachment to solid surfaces
- consists of the capsule and slime layer
What are the three main components that make up the flagella ?
Three parts, made of protein flagellin:
- Filament: outermost region
- Hook: attaches to the filament
- Basal body: consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane
What is a sensory organelle ?
One which detects chemical changes and temperature changes
What are fimbriae ?
Fimbriae (1-500 per bacteria)
Thin hairlike appendages that allow for attachment
Some types are involved in a twitching motility
What are the sex pili ?
Sex Pili
Hair-like tubular structure
Conjugation pili involved in DNA transfer from one cell to another
