Assalamualaikum :)
Today we learn about Microbial Groups. I think I like this topic because it's quiiet easy to understand and of course because the lecture note thinner than others. Okay, let's get started! Before this, I think to indicate microbial growth, we have to look at the size of population or individual growth. But that's was wrong. Microbial growth is based on size of population. Did you know the methods of microbial reproduction? There is 5 which are binarry fission, budding, fragmentation, formation of spores and sexual reproduction.
The terms pure culture is only use in the laboratory because microorganisms do not grow as pure culture in the environment but it's exist as microbial community out there. Then, we go through requirements for development of microbial community. Firstly, physical growth requirements are light, temperature, pH, water activity and osmotic pressure. Microbes that need light we call it as phototroph because it undergo photosynthesis to produce glucose. The lower density of light, lower phototrophs while in terms of wavelenght, it depends on photopigments. Based on the notes, I don't really understand what is meant by require/kill by light. Later I will ask Dr. Wan. Secondly, temperature will affects microbial reproduction. There are 3 groups of microbes:
a. Mesophiles (25-40 C)
b. Psychrophiles ( <0 C but optimal at 15C)
c. Psychrotrophs (optimal at 20-30 C)
d. Thermophiles (optimal 45 C - 50 C or higher)
Next is pH. Most bacteria can grow in pH 5-9 while fungi from pH 2-9. Very important to differentiate between Acidophiles and Alkaliphiles. Acidiphiles can survive in extreme low pH like archaebacteria while alkaliphiles prefer alkaline condition.
Water activity and osmotic pressure also important to make water movement. Water is very necessary for growth. What's difference between bacteria and fungi is in their habitat. Higher water activity for bacteria and vice versa. What is osmosis? It is diffusion of fluid through a semipermeable membrane from high concentration of water to low concentration of water. Osmotic pressure is needed to make froce to drive water movement. In addition,
 |
| Hypertonic --> Plasmolysis; Hypotonic --> Lysis |
That's all for today. BYE :)
MAY 1, 2015; FRIDAY
We continue the lecture on topic Microbial Group with second requirement which is chemical growth requirement which are water, carbon, oxygen, nitrogen phsphorus sulfur, special growth factors and trace elements. Basically, water constitutes 75-90% of cell except endospores! Water play the roles to dissolve nutrients and and make cellular functions. Next, carbon as building block and the main source of energy while oxygen is needed for aerobic microbes to survive. Also, for microaerophiles that require little amount of it and facultative anaerobes.
Nitrogen, Phosphorus, and sulfur is required for biosynthesis of proteins, nucleic acids and other biomolecules. Nitrogen can be obtain from atmosphere, ammonim ions, nitrate ions or organic source while phosphorus and sulfur from inorganic and both inorganic and organic molecules respectively. Besides, speacial growth factors is specifically neede for growth of certain microorganisms such as Legionella pneumophila that bring Legionaires' disease. .Absolute requirement for a.a. L-cystein and iron but in nature, it is provided by algae and amoebas. Iron, magenesium, copper, zinc... are some of examples of trace minerals. It is microorganism dependant and very important fro enzyme function.
Inprevious entry, I already mention about Nutritional groups so I think it should be in our mind. Next, populations are compete to occupy niches. Each successful population plays a functional role and contributes to the maintenance of teh community. Basically, first population to arrive have selective advantage, in over time, there may be population succession.
Before that, did you know what is niches?
"A niche is a term that is used in ecological biology to define an organism's role in an ecosystem. Not only does a niche include the environment a given organism lives in, it also includes the organism's "job" in that environment. A niche may also encompass what the organism eats, how it interacts with other living things or biotic factors, and also how it interacts with the non-living, or abiotic, parts of the environment as well.
All living organisms have what is called a fundamental niche. This is all of the possibilities available for the organism to take advantage of. All possible sources of food, all open roles in the environment, and any suitable habitat is included in a fundamental niche.
In reality, an organism is not going to use all suitable resources in an environment at the same time. Instead, an organism will have a narrower range it will use. This more specific role is called the organism's realized niche."-By Heather Scoville; Evolution Expert; http://evolution.about.com/
In microbial diversity, the higher the better to stablilize a habitat, have overlapping niches and functions.
What is meant by succession?
"The word succession was first used by the French naturalist Adolphe Dureau de la Malle to refer to the vegetation development after forest clear-felling.
Ecological succession has an essential role in changing the composition or structure of a community. For instance, a new community of forest trees introduces shade to its ecosystem, or a previous community of vegetation that changed the fertility of the soil.
Succession may arise from the formation of new, unoccupied habitat such as a lava flow or a severe landslide. This kind of succession in which the sequential development of plant or animal communities in an area where no soil initially exists is called primary succession. Succession may also be initiated by a disturbance of an existing community like fire, severe windthrow and logging. This kind of succession where communities develop in areas where soil already exists is called secondary succession."-
I think that's all for now. Good bye!
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