bacteria characteristics

flagella

Some bacteria also have tail-like structures called flagella ( Figure 1.3). Flagella help bacteria move. As the flagella rotate, they spin the bacteria and propel them forward. It is often said the flagella looks like a tiny whip, propelling the bacteria forward. Though some eukaryotic cells do have a flagella, a flagella in eukaryotes is rare. The flagella facilitate movement in bacte- ria. Bacteria may have one, two, or many flagellaor none at all.

textbook_image

size and shape

Bacteria are so small that they can only be seen with a microscope. When viewed under the microscope, they have three distinct shapes ( Figure 1.1). Bacteria can be identified and classified by their shape: 1. Bacilli are rod-shaped. 2. Cocci are sphere-shaped. 3. Spirilli are spiral-shaped. Bacteria come in many different shapes. Some of the most common shapes are bacilli (rods), cocci (spheres), and spirilli (spirals). Bacteria can be identified and classified by their shape.

textbook_image

similarities to eukaryotes

Like eukaryotic cells, bacterial cells have: 1. 2. 3. 4. Cytoplasm, the fluid inside the cell. A plasma or cell membrane, which acts as a barrier around the cell. Ribosomes, in which proteins are put together. DNA. By contrast though, bacterial DNA is contained in a large, circular strand. This single chromosome is located in a region of the cell called the nucleoid. The nucleoid is not an organelle, but a region within the cytoplasm. Many bacteria also have additional small rings of DNA known as plasmids. See bacterial cell pictured below ( Figure 1.2). The structure of a bacterial cell is dis- tinctive from a eukaryotic cell because of features such as an outer cell wall, the circular DNA of the nucleoid, and the lack of membrane-bound organelles.

textbook_image

unique features

Bacteria lack many of the structures that eukaryotic cells contain. For example, they dont have a nucleus. They also lack membrane-bound organelles, such as mitochondria or chloroplasts. The DNA of a bacterial cell is also different from a eukaryotic cell. Bacterial DNA is contained in one circular chromosome, located in the cytoplasm. Eukaryotes have several linear chromosomes. Bacteria also have two additional unique features: a cell wall and flagella. Some bacteria also have a capsule outside the cell wall.

the cell wall

Bacteria are surrounded by a cell wall consisting of peptidoglycan. This complex molecule consists of sugars and amino acids. The cell wall is important for protecting bacteria. The cell wall is so important that some antibiotics, such as penicillin, kill bacteria by preventing the cell wall from forming. Some bacteria depend on a host organism for energy and nutrients. These bacteria are known as parasites. If the host starts attacking the parasitic bacteria, the bacteria release a layer of slime that surrounds the cell wall. This slime offers an extra layer of protection.

characteristics of bacteria

Bacteria are the most successful organisms on the planet. They lived on this planet for two billion years before the first eukaryotes and, during that time, evolved into millions of different species.

instructional diagrams

No diagram descriptions associated with this lesson

questions

bacteria are the most successful organisms on the planet.

-->  a. true

b. false

bacteria were the first types of life to evolve.

-->  a. true

b. false

what structure helps the bacteria move?

a) the pili

b) the plasmid

-->  c) the flagella

d) the tail

the bacterial cell wall is made of peptidoglycan, a molecule of

a) sugars and nucleic acids.

-->  b) sugars and amino acids.

c) phospholipids and amino acids.

d) phospholipids and proteins.

which best describes bacterial dna?

-->  a) one round chromosome

b) one long chromosome

c) 23 pairs of chromosomes

d) 46 chromosomes

which best describes the location of the bacterial dna?

a) bacterial dna is located in the nucleus.

-->  b) bacterial dna is located in the nucleoid.

c) bacterial dna is located in the cytoplasm.

d) bacterial dna is located in the middle of the cell.

what is located outside the cell wall of some bacteria?

a) the cytoplasm

b) the plasma membrane

-->  c) the capsule

d) the outer wall

diagram questions

No diagram questions associated with this lesson