Taxonomy, Structure, Physiology

Question 1

What can bacteria be classified as medically?

Answer 1

Medically speaking, bacteria can be classified as:
– Frank Pathogens
• Capable of causing disease in any host; always considered a pathogen when isolated
– Opportunistic Pathogens
• Capable of causing disease given the opportunity; often a
commensal and part of the normal host flora, but is capable of causing disease in normally sterile tissues (most pathogens fall into this group)
– Non-pathogens
• However, even weak or non-pathogenic bacteria can cause
disease in hosts with weakened immune systems

Question 2

What is a frank pathogen?

Answer 2

Capable of causing disease in any host; always considered a pathogen when isolated

Question 3

What is an opportunistic pathogen?

Answer 3

Capable of causing disease given the opportunity; often a
commensal and part of the normal host flora, but is capable of causing disease in normally sterile tissues (most pathogens fall into this group)

Question 4

What is a non pathogen?

Answer 4

However, even weak or non-pathogenic bacteria can cause
disease in hosts with weakened immune systems

Question 5

What is the formula for virulence and resistance?

Answer 5

D= N*V/R
Disease
Number of organisms
Virulence of the organism
Resistance

Question 6

What is the purpose of artificial classification schemes?

Answer 6

Bacterial classification schemes are artificial in order to:

• speed up the identification process
• identify bacteria using a limited # of characteristics

Question 7

What is involved in bacterial nomenclature?

Answer 7

Bacterial nomenclature involves use of

• binomial system to assign a genus and species
• specific conventions for naming
• Example: Salmonella cholerasuis

Question 8

What is bacterial identification normally based on?

Answer 8

• morphological, biochemical and serological “traits”
• other: nucleic acid profile (DNA/RNA)

Question 9

What are the cell arrangements/ division planes?

Answer 9

• Diplococci
• Streptococci
• Tetrad
• Sarcinae
• Staphylococcus

Question 10

What are the parts of a procaryotic cell?

Answer 10

Question 11

What are the parts/ steps to bacterial spores?

Answer 11

Question 12

What are gram negative and positive bacteria? What is their characteristic differences?

Answer 12

• The terms gram-positive and gram-negative refer to the color of the bacteria after Gram staining.
• Gram-positive bacteria have a thick peptidoglycan cell wall and appear blue/violet.
• Gram-negative bacteria have a thin peptidoglycan wall, but have a –lipid-rich outer membrane, and appear red after Gram staining.

Question 13

How do you make a gram stain?

Answer 13

• Make a THIN smear from a pure culture on a slide and heat-fix.
• Cover smear with crystal violet; let stand for 30 sec.-1 min. Rinse.
• Cover smear with Gram’s iodine (mordant); let stand for same amount of time. Rinse.
• Hold slide at an angle and rinse with alcohol or alcohol-acetone until blue runs off. Rinse.
• Cover smear with safranin for 30 sec.-1 min. Rinse, blot dry, and examine under oil immersion at 100X.

Question 14

What are Lipopolysaccharides?

Answer 14

Lipopolysaccharide (LPS) – LPS is also known as endotoxin, and is the predominant lipid in the outer leaflet of the outer membrane of the Gram-negative cell. LPS acts as the prototypical endotoxin because it binds theCD14/TLR4/MD2 receptor complex, which promotes the secretion of pro-inflammatory cytokines in many cell types, but especially in macrophages.

Question 15

What is flagella?

Answer 15

Flagella - filamentous appendages ( 2-20 um) composed of
flagellin monomers; allow for motility; “H” antigens can be
detected with specific antibodies.
Flagella and pili may be glycosylated proteins.

Question 16

What is a glycocalyx?

Answer 16

Glycocalyx – capsule or slime layer that is composed of
carbohydrates or glycoproteins; not necessary for growth, but
inhibits phagocytosis and antibiotic uptake; antigenic when on
cell and “K” antigens can be detected with specific antibodies.

Question 17

What is pili?

Answer 17

Pili - filamentous appendages (0.5-2.0 um) composed of pilin
monomers; allow for adhesion (fimbriae) and specialized sex pili
allow for transfer of DNA between a donor and a recipient; highly
antigenic and antibodies can be used for sero-diagnosis.

Question 18

What physical conditions affect growth of an organism?

Answer 18

Temperature

Gaseous Requirement

pH

Question 19

What are the pathways of energy production in bacteria?

Answer 19

1. ) Fermentation (anerobic process) (Glycolysis)
2. ) Respiration
3. ) Photosynthesis

Question 20

What are the nutritional classification of organisms?

Answer 20

• Photoautotroph: (self feeding) (light energy source, CO2 carbon source)
• Photoheterotroph: (light compounds energy source, organic nonsulfur compounds carbon source)
• Chemoautotroph: (energy is from inorganic compounds, carbon souce is CO2)
• Chemoheterotroph (energy is from organic compounds, carbon source is organic compounds)

Question 21

What is an example of photoautotroph?

Answer 21

Photosynthetic bacteria

Question 22

What is an example of Photoheterotroph?

Answer 22

Purple and green bacteria

Question 23

What is an example of an Chemoautotroph?

Answer 23

Hydrogen, nitrogen, iron, and nitifying bacteria

Question 24

What is an example of an Chemoheterotroph ?

Answer 24

Most bacteria, all fungi, protozoans, and animals

Question 25

What are the bacterial classifications based on gaseous requirements?

Answer 25

• Most bacteria associated with animals grow only in the presence of air, only anaerobically, either (facultatively), or in CO2 and are able to ferment or oxidize sugars. - Ex exoli, pasteurella, staphylococcus - These bacteria are facultative anerobes ( fermenters or acid formers,) but normally grow better in air. • Some bacteria are aerobes and only oxidize sugars (no acids) – e.g. Pseudomonas, Aeromonas, Acinetobacter • Some bacteria are aerobes, but do not utilize sugars at all – e.g. Bordetella, Moraxella – These bacteria utilize nitrogen, sulfur, or other electron acceptors from amino acids or other compounds other that sugars. • Some bacteria only grow well in the presence of low quantities of oxygen (3%) (microaerophilic) – e.g. Campylobacter jejuni • Some bacteria only grow in air with additional carbon dioxide (capnophilic) – e.g. Haemophilus • Some bacteria only grow in the absence of air and only ferment sugars (anaerobic) – e.g. Bacteroides

Question 26

What are the types of bacterial culture medium? What are examples of bacterial culture medium used for isolation and identification?

Answer 26

* Defined/ simple (e.g. minimal salts) * Enriched/complex (e.g. nutrient broth) Isolation and Identification 1. Differential media (e.g. MacConkey agar) 2. Selective media (e.g. Selenite broth) 3. Enriched media (e.g. Blood agar) 4. Transport media (e.g. Stuart’s media)

Question 27

What is metabolism?

Answer 27

Metabolism is the net result of biochemical activities associated with catabolic and anabolic pathways - leading to growth.

Question 28

What is synonymous with energy generation? How can it occur?

Answer 28

• ATP is synonymous with energy generation - can occur by photosynthesis, respiration or fermentation.

Question 29

Most bacteria are.....

Answer 29

Most bacteria are chemoheterotrophs.

Question 30

What is the benefit of characterizing by products of metabolism?

Answer 30

• The characterization of by-products associated with metabolism can be used to identify bacteria e.g. “metabolic footprint” (API 20E).

Question 31

What are the incubation conditions?

Answer 31

- Temperature, Gas, and pH These factors can significantly influence the rate at which bacteria grow.

Question 32

What can culture media be designed to do?

Answer 32

• Culture media can be designed to facilitate growth as well as transport and identification of bacteria.

Question 33

Common initial methods of identification are based on whether bacteria are?

Answer 33

– Fermentative – Oxidative – Nonoxidative (doesn’t utilize sugars) – Microaerophilic – Anaerobic – Aerobic – Capnophilic