chapter 7 bacteria and viruses. chapter 7 lesson 1 what are bacteria?
TRANSCRIPT
Bacteria are microscopic prokaryotes (they do not have a nucleus).
Bacteria live in almost every habitat on Earth and in or on almost every organism, both living and dead.
Characteristics of Bacteria
bacteria
from Greek bakterion, means “small staff”
• A typical bacterium consists of DNA and cytoplasm surrounded by a cell membrane and a cell wall.
• Most bacteria have DNA that is one coiled, circular chromosome.
• Many bacteria also have one or more small circular pieces of DNA called plasmids that are separate from their other DNA.
Characteristics of Bacteria (cont.)
• Bacteria are much smaller than plant or animal cells.
• They have one of three basic shapes:
• round or sphere (cocci)
• Rod (bacilli)
• Spiral (spirilli)
Characteristics of Bacteria (cont.)
• single-cell organisms with no nucleus (prokaryote.)
3 common shapes
CocciCocci- -
roundroundBacilliBacilli--
rod shapedrod shaped
SpirillaSpirilla- -
spiral shapedspiral shaped
• Bacteria live in many different places and obtain food in various ways.
• Some bacteria take in nutrients from dead organisms or living hosts.
• Some bacteria make their own food using energy from light or chemical reactions.
Characteristics of Bacteria (cont.)
• Bacteria that can live where there is no oxygen are called anaerobic.
• Bacteria that need oxygen are called aerobic.
Characteristics of Bacteria (cont.)
Some bacteria are able to find their resources by moving around with special whiplike structures called flagella.
Characteristics of Bacteria (cont.)
• Bacteria reproduce asexually by fission- cell division that forms two genetically identical cells.
• Genetic variation can be increased by a process called conjugation, in which two bacteria of the same species attach to each other and combine their genetic material.
• An endospore forms when a bacterium builds a thick internal wall around its chromosome and part of the cytoplasm.
• An endospore can protect a bacterium from intense heat, cold, or drought.
• Endospores can remain dormant for months or even centuries.
Endospores
• Prokaryotes called archaea are similar to bacteria, but the ribosomes of archaea more closely resemble the ribosomes of eukaryotes than those of bacteria.
• Archaea contain molecules in their plasma membranes that are not found in any other known organisms and often live in extreme environments such as hot springs and salt lakes.
Archaea
Kingdom Archaebacteria
• Live where no other living things are found
– Ex: hot springs, beneath ice in Antarctica, volcanic vents
• 3 main types
– Salt lovers
– Heat lovers
– Methane makersThe yellow coloring in the water at the Midway Geyser Basin in Yellowstone National Park is caused by archaebacteria. Archaebacteria are known to surviveat extremely high temperatures like those produced from a geyser.