phale
Posts: 10
Joined: Sun Nov 11, 2007 11:05 am

Can someone help me with these biotechnological problems?

Postby phale » Sun Nov 11, 2007 11:18 am

I'm doing a research called "Gathering bacteria" at school. My teacher, Mrs.Berres has mentioned about bacterial lawn and bacterial colony but I didn't get it. My question is "What is the difference between a colony of bacterial growth and a lawn of bacterial growth?". Please help me with this. It'd be very kind of you to post some example pictures if available.
I have another question "How to tell a fungal from bacterial growth?"
I appreciate your help. Thank you
Phale

Louise
Former Expert
Posts: 921
Joined: Mon Jan 16, 2006 2:17 pm

Re: Can someone help me with these biotechnological problems

Postby Louise » Sun Nov 11, 2007 11:33 am

phale wrote:I'm doing a research called "Gathering bacteria" at school. My teacher, Mrs.Berres has mentioned about bacterial lawn and bacterial colony but I didn't get it. My question is "What is the difference between a colony of bacterial growth and a lawn of bacterial growth?". Please help me with this. It'd be very kind of you to post some example pictures if available.
I have another question "How to tell a fungal from bacterial growth?"
I appreciate your help. Thank you


Hi,
We cannot post pictures, only link to pictures we find on the web. A lawn is just when you have so many colonies they blur together in to a matt (or lawn!) instead of being individual colonies.

I think you should look at the microbiology section of science buddies.

http://www.sciencebuddies.com/mentoring/project_ideas/home_MicroBio.shtml?from=Home

On the right hand side there are "related links". I think they will be very helpful to you, specifically:
http://www.sciencebuddies.com/mentoring/project_ideas/MicroBio_Interpreting_Plates.shtml


Louise

donnahardy2
Expert
Posts: 2671
Joined: Mon Nov 14, 2005 12:45 pm

Bacterial colonies and lawns

Postby donnahardy2 » Sun Nov 11, 2007 11:58 am

Hi Phale,

Bacteria are very small organisms, about 1 micron, and only visible individually through a microscope. Bacteria are usually grown on a solid agar medium, and one cell will double every 20-30 minutes under ideal conditions and grow to a visible dot on the agar surface called a colony, which contains millions of bacteria. If you are gathering bacteria from various surfaces at school and transferring them to a nutrient agar plate, the individual dots that are visible after 24 or more hours of incubation on the agar plate are called colonies, and each colony represents the bacteria grown from a single cell.

There's only room for about 100-200 individual colonies to grow on a nutrient agar plate, so if there are more bacteria placed on the agar to grow, the colonies will grow together and the surface of the agar plate will be completely covered with a continuous growth, or lawn of bacteria. Lawns of bacteria can be used to measure the effect of chemicals on the growth of bacteria. For example, if you make a lawn of bacteria taken from a single colony, and place small paper discs containing antibiotics on the lawn before incubation, the inhibition of growth around the disc can be used to measure antibiotic resistance or susceptibility of the bacterium.

Bacterial colonies are usually have a smooth and creamy appearance, but can have various colors and textures. Fungi are always furry; they are white in the beginning, and then turn dark green, black, or brown as they form spores. I'm sure you are familiar with the appearance of bread mold or moldy cheese.

I hope this helps.

Donna Hardy

phale
Posts: 10
Joined: Sun Nov 11, 2007 11:05 am

Re: Bacterial colonies and lawns

Postby phale » Sun Nov 11, 2007 5:39 pm

donnahardy2 wrote:Hi Phale,

Bacteria are very small organisms, about 1 micron, and only visible individually through a microscope. Bacteria are usually grown on a solid agar medium, and one cell will double every 20-30 minutes under ideal conditions and grow to a visible dot on the agar surface called a colony, which contains millions of bacteria. If you are gathering bacteria from various surfaces at school and transferring them to a nutrient agar plate, the individual dots that are visible after 24 or more hours of incubation on the agar plate are called colonies, and each colony represents the bacteria grown from a single cell.

There's only room for about 100-200 individual colonies to grow on a nutrient agar plate, so if there are more bacteria placed on the agar to grow, the colonies will grow together and the surface of the agar plate will be completely covered with a continuous growth, or lawn of bacteria. Lawns of bacteria can be used to measure the effect of chemicals on the growth of bacteria. For example, if you make a lawn of bacteria taken from a single colony, and place small paper discs containing antibiotics on the lawn before incubation, the inhibition of growth around the disc can be used to measure antibiotic resistance or susceptibility of the bacterium.

Bacterial colonies are usually have a smooth and creamy appearance, but can have various colors and textures. Fungi are always furry; they are white in the beginning, and then turn dark green, black, or brown as they form spores. I'm sure you are familiar with the appearance of bread mold or moldy cheese.

I hope this helps.

Donna Hardy
Phale

kathleenkimball4
Former Expert
Posts: 8
Joined: Mon Nov 05, 2007 8:52 pm

Postby kathleenkimball4 » Mon Nov 12, 2007 8:52 pm

A bacterial colony is when there are small, little groups of bacterial living together apart from other bacterial colonies. I like to think of them as freckles on the agar. Here is a picture:
http://www.sciencehound.com/science_pro ... e-5333.gif
Bacteria lawn is where the whole surface looks like one colony, just like a grass lawn. Here is a picture:
http://www.bmb.leeds.ac.uk/mbiology/ug/ ... leming.jpg

Your question is very interesting! You should test common types of fungus and bacteria. Your teacher can help you find safe kinds that won't be too dangerous to grow. Pictures always help when finding the difference, but you can also talk about their microscopic differences. Which one is the more complex organism? Which one grows faster?
Things like that can help you differentiate between them. :)
-Kathleen-

TroyPercival
Former Expert
Posts: 62
Joined: Tue Sep 18, 2007 7:11 pm

Differentiating fungus and bacteria

Postby TroyPercival » Tue Nov 13, 2007 12:21 am

Fungi are generally classified as molds or yeasts, mold on petri dish look exactly like those that grow on your bread at home, which have a fuzzy or wooly appearance, while yeast give a similar appearance comparing to bacteria colony on Petri dish. An experience microbiologist will be able to tell whether the colony is bacteria or yeast in seconds, by its morphology and a couple basic biochemical tests. The easiest way for you to find out whether the colony is yeast or bacteria is to do a gram stain. You can get a sterile loop to pick up the colony and smear it onto a slide and do the stain. Fungus will stain purple and will look much larger than bacteria under a microscope. Remember that gram positive bacteria will stain purple, while gram negative bacteria will stain pink.

Here is what yeast look like under a microscope:

https://courses.stu.qmul.ac.uk/smd/kb/p ... cyeast.jpg

Here is what a gram positive bacteria look likes under a microscope with the same magnification.

https://courses.stu.qmul.ac.uk/smd/kb/p ... cstrep.jpg

TroyPercival
Former Expert
Posts: 62
Joined: Tue Sep 18, 2007 7:11 pm

Colony Vs Lawn

Postby TroyPercival » Tue Nov 13, 2007 12:38 am

Hello, when your teacher mention colony and lawn, I think what she is referring to is the characteristic how bacteria grow. Most bacteria grow in colony format and colonies will only appear on areas of the plate that were streak on and it look like small white circle on petri dish.

http://biomarker.cdc.go.kr:8080/pathoge ... r(colony-1).JPG

But for swarming (lawn) growth, it will look like a hazy blanket of growth that extend beyond the area you made the streaking.

http://www.microbelibrary.org/microbeli ... 20fig9.jpg


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