Question

Chapter 4(microbiology)

1. What are the shapes and arrangements of bacteria cells?

2. Why is it important to be able to identify the shape and arrangement of an unknown bacterial sample?

3. Differentiate between eubacteria and archaebacteria.

4. What are the differences between eukaryotes and prokaryotes?

5. Why would a microbiologist care about those differences? Be specific.

6. What are the basic parts of a prokaryote? (the parts found in all bacteria)

7. How do the cell walls of Gram positive and Gram-negative organisms differ? How does this affect the result of the gram stain?

8. Describe the following bacterial “add-on parts”: What advantage do they give bacteria?

            1. flagella

2. pili
3. capsule
4. endospore
5. fimbrae
6. slime layer

9.   What is the structure of a plasma membrane?
10. What are the different types of flagellar arrangements called?
11. How is a vegetative cell related to an endospore?
12. What is diffusion, osmosis, and active transport? What would happen to a bacterial cell in a hypertonic solution?
13. What are inclusions in bacteria? What is the main purpose of inclusions?
14. What is quorum sensing? How does it contribute to pathogenicity?

Answer 1

1.There are 3 basic shapes of bacterial cells:Coccus,Rod or Bacillus and Spiral.

Arrangements of Bacterial Cells:

Cocci bacteria exist single, in pairs (diplococci), in groups of four (tetrads ),in chains (streptococci ), in clusters (stapylococci ), or in cubes consisting of eight cells (sarcinae). Cocci may be oval, elongated, or flattened on one side. Cocci may remain attached after cell division.

Bacillus Bacteria he cylindrical or rod-shaped bacteria,arranged in chains,ovoid,palisade arrangement .Bacillus cereus, lebsiella rhinoscleromatis

Spiral Bacteria are curved bacteria which can range from curved shape,corkscrew-like spiral to long, slender, and flexible.They are rigid and capable of movement

2.Bacteria are classified and identified to distinguish among strains and to group them by criteria of interest to microbiologists and other scientists. to characterize a disease outbreak, identification of toxins.Clinical microbiologists are interested in the serotype, antimicrobial resistance pattern, and toxin and invasiveness factors .Geneticians classify with specific mutations and plasmids.Identification is done to verify the authenticity or utility of a strain or a particular reaction, or to isolate and identify the organism that causes a disease.

3.Archae are single cell and have simple structure where as eubacteria have complex structure,

archae shape:spheres,rods,plates,spiral,flat,square where as eubacteria exist in cocci,rod and spiral in shape

Diameter:Archae(0.1-15microm),eubacteria(0.5-5microm)

Cellwall:Eubacteria(muramic acid),whereas Archae doesnt contain muramic acid

Thymine content:Archae(Absent) whereas present in eubacteria

RNA Polymerase Core:Archae(10subunits),Eubacteria(4 subunits)

Methanogenesis:Archae(Absent),eubacteria(present)

4.Differences between Eukaryotes and prokaryotes:

Nucleus:Eukaryotes(Present),prokaryotes(absent)

Cell type:Eukaryotes(Multicellular),prokaryotes(unicellular)

Organelles(Lysosymes,Mitochondria,Microtubules,Endoplasmic Reticulum, Cytoskeleton ): Eukaryotes (Present), Prokaryotes (absent)

Cell size:Eukaryotes(10-100microm),prokaryotes(1-10microm)

Histones:Eukaryotes(Present),Prokaryotes(absent)

Ribosomes:Eukaryotes(80s),prokaryotes(70s)

5.Microbiologists should know the differences between prokaryotes and eukaryotes in order to do research,cloning,characterize a disease outbreak or toxins identification,antimicrobial resistance pattern, studies pertaining to mutations or to isolate and identify the organism that causes a disease.

6.Basic parts of prokaryotes are Plasma membrane,cytoplasm,Ribosomes,Genetic Material,Flagella

7.Peptidoglycan:Gram positive(thick),gram negative(thin)

Periplasmic space:Gram positive(absent),gram negative(present)

Lipopolysaccharide content:Gram positive(absent),gram negative(present)

Flagella:Gram positive(2 rings),gram negative(4 rings)

Lipid and lipoprotein content:Gram positive(low),gram negative(high)

Cell wall:Gram positive(100-120A),gram negative(70-120A)

Mesosome prominence:Gram positive(more),gram negative(less)

8.1.Flagella:Bacterial Movement and thereby bacteria uses to find food

2.Pili:Provides attachments between bacterial cells

3.Capsule:protects the bacteria against desiccation.

4.Endospore:survival of a bacterium through periods of environmental stress.

5.Fimbrae:Adherence,adhere to one another

6.Slime layer:protect the cells from environmental dangers such as antibiotics and desiccation.

7.Structure of plasma membrane:Composed of a phospholipid bilayer with embedded proteins

8.Different types of flagellar arrangements:Monotrichous,Amphitrichous,Lophotrichous,Peritrichous

9.Normally growing cell that forms the endospore is called a vegetative cell.

10.Diffussion:movement of a substance from an area of high concentration to an area of low concentration.

Osmosis:molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one.

Active transport:movement of ions or molecules across a cell membrane into a region of higher concentration

11.Bacterial inclusions are discrete structures seen within the confines of prokaryotic cells,function as metabolic reserves, cell positioners, or as metabolic organelles.

12.Quoram sensing is to minimize host immune responses by delaying the production of tissue damaging virulence factors