Unit 1, Lecture 4.2

Describe the structure of bacterial ribosomes.

50S and 30S subunits

Botulism is caused by Clostridium botulinum, a bacterium that is normal flora of the intestinal tract of grazing animals. A person home-canned some green beans by boiling the beans and placing them in jars and screwing on lids. The lids popped down indicating a vacuum had formed within the jar. Upon ingesting these beans the person contracted botulism. Based on what was learned about Clostridium, explain.

Endospores of Clostridium botulinum, an obligate anaerobe, leave the intestinal tract of the animal through defecation and survive in the soil. The endospores that contaminate the beans are resistant to boiling and survive. Once the vacuum is created within the jar, the environment is anaerobic. The spores are able to germinate in the food under these anaerobic conditions. As the vegetative bacteria replicate in the food they secrete an exotoxin that causes botulism.

Describe the function of bacterial ribosomes .

Ribosomes function as a workbench for protein synthesis, that is, they receive and translate genetic instructions for the formation of specific proteins

Dormant resistant survival forms produced by Bacillus and Clostridium species that resist high temperatures, most disinfectants, low energy radiation, and drying best describes:

an endospore

Briefly discuss the function of a bacterial endospore.

A bacterial endospore is not a reproductive structure, but rather a dormant, resistant, survival form of a bacterium.

Obligate aerobe, often lives in the soil, and produces endospores.

Bacillus

Obligate aerobe, often lives in the soil, and produces endospores. This best describes the genus:

Bacillus

Which genera of bacteria is an obligate aerobe?

Bacillus

Name 2 common genera of bacteria capable of producing endospores and state which is an obligate anaerobe.

Bacillus species Clostridium

Which genera of bacteria is an obligate anaerobe?

Clostridium

In terms of protein synthesis, briefly describe the process of translation

During this process, specific tRNAs pick up specific amino acids, transfer those amino acids to the ribosomes, and insert them in their proper place according to the mRNA message

What is obligate anaerobe?

Grows only in the absence of oxygen

What is the definition of obligate aerobes ?

Grows only in the presence of oxygen.

State, in a general sense, how antibiotics like neomycin, tetracycline, doxycycline, erythromycin, and azithromycin affect bacterial growth

It interferes with translation

If an antibiotic such as tetracycline binds to a 30S ribosomal subunit, how does it harm the bacterium?

It interferes with translation.

Function of mRNA

Messenger RNA copies the genetic information in the DNA by complementary base pairing and carries this message to the ribosomes where the proteins are assembled

Function of rRNA

Ribosomal RNA and ribosomal proteins form the ribosomal subunits

Describe the chemical composition of bacterial ribosomes.

Ribosomes are composed of ribosomal RNA (rRNA) and protein

Name three infections that may be transmitted to humans by endospores.

Tetanus Gas Gangrene Anthrax

The tetracyclines (tetracycline, doxycycline) are antibiotics that bind to the 30S subunit of bacterial ribosomes. The macrolides (erythromycin, azithromycin, clarithromycin) are antibiotics that bind to the 50S subunit of bacterial ribosomes. Why won't these antibiotics be effective for fungal, protozoal, or viral infections?

The antibiotics mentioned above will bind to 30S or 50S ribosomal subunits and block bacterial protein synthesis but will not bind to the 60S or 40S ribosomal subunits found in eukaryotic cells.

Describe the structure of a bacterial endospore.

The completed endospore consists of multiple layers of resistant coats (including a cortex, a spore coat, and sometimes an exosporium)

Define germination

The emergence of a vegetative bacterium from an endospore

Define sporulation

The formation of an endospore within a bacterium

In terms of protein synthesis, briefly describe the process of transcription

The process by which RNA is synthesized by complementary base pairing of ribonucleotides with deoxyribonucleotides to match a portion of one strand of DNA (a gene)

State, in a general sense, how antibiotics like neomycin, tetracycline, doxycycline, erythromycin, and azithromycin affect bacterial growth

These antibiotics bind to either a 30S or a 50S ribosomal subunit and cause faulty protein synthesis.

Function of tRNA

Transfer RNAs picks up specific amino acids, transfers the amino acids to the ribosomes, and insert the correct amino acids in the proper place according to the mRNA message.

The emergence of a vegetative bacterium from an endospore is called ________________.

germination