Lesson 6 (26/9/14)

Date : 26/9/14

Topic : External structure of prokaryotes

Activities
1. Class mind map for external and internal structures of prokaryotes

Notes

Species of microbes

• Myxobacteria (some of the prokaryotes that have multicellular stages ; myxo = mucus-related)
• Proteus microbilis (cause UTI disease, usually G-, has swarm-like motility)
• Treponema pallidum (a spirochete bacterium that cause treponemal diseases - syphilis, bejel, pinta, yaws ; only visible using dark field microscope)
• Borrelia burgdorferi (spirochete that causes Lyme disease)
• Epulopiscium fishelsoni (G+ bacteria that have symbiotic relationship with surgeonfish)
• Corynebacteria diphtheriae (bacterium that causes diphteria ; pleomorphic)
• Mycoplasma (bacteria that lack a cell wall, thus unaffected by antobiotics like penicillin that target cell wall synthesis)
• Mycoplasma pneumoniae (cause mycoplasma pneumonia_
• Mycoplasma genitalium (cause gential diseases such as urethritis, cervictis, pelvic inflammation)
• Ureaplasma
• Pyrolobus fumarii (archaea - survive at high temperature like hydrothermal vent)
• Thermoplasma (facultative archaea - survive in  acidic and high-temperature environments)

Terms in microbiology

• Glycocalyx (organized and firmly attached to cell wall - capsule ; unorganized and loosely attached to cell wall - slime ; made of sugar called EPS - extracellular polysaccharide)
• Extracellular polysaccharides, EPS (sugars that made glycocalyx ; also a main substrate of biofilm ; biofilm = indicator of pollution level)
• Flagella (for motility, attachment, and might be virulence factors)
• Axial filaments (normally with spiral shape, wrap around the cell ; consist of protein pilin arranged helically around a central core)
• Fimbriae (short, thin and straight appendages ; help cells adhere to surfaces)
• Sex or conjugation pili (short, thin and straight appendages ; for transfer of DNA from one cell to another)
• Chemotaxis (movement of organism in response to chemical stimulus - e.g. antibiotics)
• Phototaxis

Random facts

• Most prokaryotes are unicellular except myxobacteria which have multicellular stages in their life cycles
• Unusual shape of bacteria is influenced by environmental conditions, age of culture and antibiotic pretreatment.
• Normally spirochetes live in water.
• Epulopiscium fishelsoni was once known as very large microbe until it's replaced by the largest microbe - Thiomargarita namibiensis.
• The size of microbes is important, one of the uses is in water filter that filter out large microbes. However, small microbes such as virus can easily pass through the filter.
• Autoclave is used to sterillize equipment and culture especially when the culture cannot be heated over high temperatures (e.g. cannot heat antibiotics over 121°C)
• Not every bacteria has capsules.
• Flagella is made of protein called flagellin and is made up of basal body, hook and filament.
• Flagella may be virulence factors because it makes bacteria motile and enables their suvival and ability to cause and spread diseases)
• Peptidoglycan / murein is made up of repeating disaccharide (NAG + NAM)
• peptido : cross-linked, amino acids (N-acetylmuramic acid)
• glycan : sugar (N-acetylglucosamine)
• Lysozyme-sensitive bond, L-Alanine and D-glutamic acid mark the difference between bacteria and archae.
• Genes are transferred from plasmid through the process of conjugation or sexual reproduction of bacteria such as E.coli.

Muddiest point

• Still kind of blurred about the size - shape relationship.                                                   

My own exploration

• Spirochetes contribute to digestion in ruminants and help in feeding in mussels and oysters (by acting as cilia to sweep food into mollusk), but also can cause diseases such as syphilis (Treponema pallidum) and Lyme disease (Borrelia burgdorferi).
• Axial filaments are present in all spirochetes except Treponema.
• Aquaspiririllum magnetotacticum has magnetic properties that allow it to orient itself in the water in relation to Earth's magnetic field

Reflection on this topic

Not so much about the topic, just a feeling that I came across recently. I couldn't manage to finish all the topics before entering the lecture because I was busy with other stuffs and kind of relaxed.I found that writing journals for the topics recently has became more difficult too. There are lots of information that I want to look up but they're just too much! I'm still trying to adapt university lifestyle of which I need to balance my academy and co-curricular activities as well as my personal life.  I need to manage time better, gotta be an efficient learner. Plus, I have to learn to be a thinker, rather than memorizing and burping out all the facts. These two are the things that I need to make adjustment.