WEEK 3

BMY3101-1 MICROBIOLOGY I

WHAT HAVE I LEARN?

Our class start with the announcement of test 1 on 27th of October. This week we are going to learn a new chapter but before that, our coursemate give us presentation on "Hydrothermal vent". I gain more information and know more about " Hydrothermal vent" from the presentation. After a 40 minutes of lecture on microscopy, we have a small quiz to test our understanding.I am so nervous because I don't even study at all on the behind part of microscopy. I only manage to score 3/5 in this quiz. I hope i can score well in the next quiz and also test 1.

ABOUT HYDROTHERMAL VENT 

• A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart at spreading centers, ocean basins, and hotspots.
• Tectonic plates are related to the lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken into tectonic plates. The Earth's lithosphere is composed of seven or eight major plates (depending on how they are defined) and many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries (or faults). The relative movement of the plates typically ranges from zero to 100 mm annually.
• Life has traditionally been seen as driven by energy from the sun, but deep-sea organisms have no access to sunlight, so they must depend on nutrients found in the dusty chemical deposits and hydrothermal fluids in which they live. 
• Hydrothermal vent communities are able to sustain such vast amounts of life because vent organisms depend on chemosynthetic bacteria for food. The water from the hydrothermal vent is rich in dissolved minerals and supports a large population of chemoautotrophic bacteria. These bacteria use sulfur compounds, particularly hydrogen sulfide, a chemical highly toxic to most known organisms, to produce organic material through the process of chemosynthesis.

Tectonic plate

• Although life is very sparse at these depths, black smokers are the centers of entire ecosystems. Sunlight is nonexistent, so many organisms – such as archaea and extremophiles – convert the heat, methane, and sulfur compounds provided by black smokers into energy through a process called chemosynthesis. More complex life forms, such as clams and tubeworms, feed on these organisms. The organisms at the base of the food chain also deposit minerals into the base of the black smoker, therefore completing the life cycle.
• A species of phototrophic bacterium has been found living near a black smoker off the coast of Mexico at a depth of 2,500 m (8,200 ft). No sunlight penetrates that far into the waters. Instead, the bacteria, part of the Chlorobiaceae family, use the faint glow from the black smoker for photosynthesis. This is the first organism discovered in nature to exclusively use a light other than sunlight for photosynthesis.

Microscopy

• Produce a magnified image of specimen ( size, structure )
• Separate the details in the imagie
• render the details visible to the human eyes or camera
• determine the interaction of microorganisms ( metabolism )
  eg: how antibiotic break the bacteria, how conjugation happening 

- Antibiotic-resistant strains of S. aureus such as methicillin-resistant S. aureus (MRSA)

- Propionibacterium is a gram-positive, anaerobic, rod-shaped genus of bacteria named for their unique metabolism: They are able to synthesize propionic acid by using unusual transcarboxylase enzymes.

These kind of bacterium is known as a "superbug," which belongs to a family of bacteria resistant to antibiotics.

Mircroscopes

Light Microscope

• Bright- field microscope 
• require stain
• produce dark image against a brighter background

A cynobacteria from a freshwater sample under bright- field microscope. ( Blue green algae )

• They are photosynthetic- produce oxygen 
• found on the surface of ocean
• producer ( source for other organism )
• phytoplankton 
• they are eaten by protozoa ( predator of bacteria )

• Dark- field microscope
• produces a bright image against a dark background
• used to observe living, unstained preparations
• used to observe internal structures in eukaryotic microorganisms

Microbial interaction 

Termite gut exhibits one of the most complex microbial communities, consisting of diverse microorganisms from all three domains of life: Bacteria, Archaea, and Eukarya.

Interaction between the microbes in the termite gut is highly mutual, usually beneficial for both microbes.

Prokaryotes are closely associated with protists as symbionts, either attached to the cell surfaces or live within the cytoplasm or nucleus of the protists. For instance, Treponema spirochete bacteria are attached to the special bracket-like structures on the plasma membrane of mixotricha and contributes to the movement of the host protist known as “motility symbiosis”(3). Treponema also benefits by living on and within the protist, easilly accessible to nutrients H₂ and CO₂ produced by mixotricha and utilize them to synthesize acetate and obtain energy for their own growth as well (5).

Another mutual relationship shown between Methanobrevibacter and parabasalids protist, H₂ plus CO₂ produced by protists also can be used by methanogens as energy source but they form methane,CH₄ in this case. Successful elimination of produced H₂ by endosymbiont’s H₂ evolution activity enables the protists to maintain optimal pH and stimulate its decomposition activity (4). These two groups of microorganism interact and work together to digest cellulose and enhance the cellulose fermentation.

Although most of the microbes act mutually, there is one exception between the relationship of methanogens and acetogens. Both take up H₂ and CO₂ as their substrates, thus they are likely to be in a compete relationship. Acetogenesis dominates methanogenesis from the same substrate, H₂ plus CO₂, because acetogenesis requires less energy loss of the termite by absorbing acetates but not methane as the energy source.(4)

• Phase-contrast Microscope 
• converts differences in refractive index/ cell density into detected variations in light density
• Excellent way to observe living cells 
• Stain is not necessary
• view internal structures of living organisms ( organelle)

• Fluorescence Microscope
• specimens usually stained with fluorochromes 
• can observe microbes whether viable or not viable (viability )
• microorganisms appear as bright objects against a dark background 

• Confocal microscopy
• creates 3D image of specimens
• numerous applications including study of biofilms
• biofilms
  - are group of microbes that can form layers
  - able to stick to certain surface
  - they will pull other microbes together form layers
  - eg: contact lenses, teeth 

Electron Microscope 

• Scanning electron microscope (SEM )
• produces a realistic 3D image of specimen's surface features
• to study the surface features of cells and viruses
• Transmission electron microscope (TEM )
• image produce 2D
• to examine viruses or the internal ultrastructure in thin sections of cell 

Results of Quiz 1