Microbiology Lecture 1 Review: Chapter 1,3 Introduction to Microbes and Structure

Lecture Review - By: Amma Genfi

Chapter 1: Humans and Microbes

1.    [01-01] What were conclusions drawn from experiments of Louis Pasteur with swan-necked flasks and experiments of John Tyndall with various broths? – Lecture 1, Slide 5 –
Louis Pasteur found that microbes can not be spontaneously generated and are present in the air. Tyndall had shown that bacteria can have heat resistant forms, these later turned out to be endospores.

2.    [01-02] Compare Archaea and Bacteria domains by discussing their similarities and differences – Lecture 1, Slide 9 – Common properties of Bacteria and Archaea include: both are unicellular prokaryotic organisms lacking nucleus and other membrane bound organelles. Both are propagating via binary fission. Differences of Bacteria and Archaea include: archaea have cell wall made of pseudopeptidoglycan, while bacterial cell wall is make of peptidoglycan. Archaea tend to live in harsh conditions like high temperature, extreme pH and salinity and, therefore, cannot cause diseases in humans. Bacteria are tending to grow mainly at moderate conditions and some of them are human pathogens.

3.    [01-03] Compare Fungi and Bacteria by discussing their similarities and differences – Lecture 1, Slide 9 –
Both Fungi and Bacteria can be Uni-Celluar and use organic source of energy. Both are Major Source of antibiotics. Differences include Fungi being a Eukaryotic while Bacteria is prokaryotic. Fungi have cell division and can do Mitosis. While bacteria undergo binary fission.

4.    [01-04] Compare kingdoms Protozoa, Plantae, Fungi, and Animalia by describing their specific properties – Lecture 1, Slide 9 –
All Eurkaryotic cells and goes through Mitosis: Meiosis. Kingdom Protista (or protozoa – simple animals) - unicellular or di-cellular organisms. Some of them are photosynthetic and have cell wall made of cellulose. Kingdom Plantae (plants) - are multicellular organisms capable of photosynthesis and have primitive tissues. The cells of these organisms have cell wall made of cellulose. Kingdom Fungi (yeasts, molds, and mushrooms) – uni- and multi-cellular organisms that can not do photosynthesis and their cells have the cell wall made of chitin Kingdom Animalia (animals) – multicellular organisms that can not do photosynthesis and their cells have no cell wall.

[01-05] Compare viruses and bacteria by describing their similarities and differences – Lecture 1, Slide 9 –
Similarities: they both are built of proteins and use nucleic acids as genetic material. Both bacteria and viruses can cause infections and diseases in humans or infect and kill bacteria. Unlikebacteria, viruses contain only one type nucleic acid, DNA or RNA, but never both. Also, viruses do not have cellular organization and are obligate parasites, while bacteria have cellular organization of prokaryotic type and may be free-living organisms.

Chapter 3: Microscope and Cell Structure

5.    [03-01] Morphology of prokaryotic cells – describe seven types of bacterial cell shapes and six types of bacterial cell grouping. Give bacterial examples – Lecture 1, Slide 22 –
Shapes
Coccus= Spherical
Coccobacillus= Rod shape, but round like coccus
Bacilus= Rod shape
Vibrio= Curved rod shape
Spirillum= Slight bends
Spirochete= Corkscrew shape
Pleomorphic= Changes shape

Groupings
Diplococcus= Double coccus groups
Streptococcus= Coccus chain
Staphylcoccus= Grape like cluster
Streptobacillus= Bacillus chain (lined up end to end lengthwise)
Palisade= Fence appearance by bacillus lined up widthwise

6.    [03-02] Describe biofilm formation by bacterial cells. Why is biofilm formed by bacterial cells can affect human health? – Lecture 1, Slide 23 –
It begins when planktonic bacteria attach to the surfaces. Additional bacteria attach and grow in the initial layer. Growing bacterial cells produce and secrete sticky material that fills the space between the cells Completely formed biofilm has open channels that allow the nutrients to move in and waste to move out of microbial community. Cells within biofilms can produce harmful chemical compounds like toxins) that can be harmful to humans. Positive can be that its used in treatment of wastewater.

7.    [03-03] Describe the general structure and functions of plasma membrane – Lecture 1, Slides 24, 25 –
Plasma (cytoplasmic) membrane is natural boundary of the cell. It is a semi-permeable structure that allows some molecules to cross, while other molecules will be prevented from crossing. Composed of Phospholipids (bilayer), proteins and sterols.

8.    [03-04] Compare the structure and properties of cell walls of Gram-positive, Gram-negative, and Acid-fast bacteria – Lecture 1, Slides 27-28 –
Gram positive Bacteria:
Thick layer of peptidoglycan is on the top of plasma (cytoplasmic) membrane.
Teichoic acids attach the cell wall to plasma (cytoplasmic) membrane.
The microbes are likely to be sensitive to penicillin.

Gram negative Bacteria:

Thin layer of peptidoglycan sandwiched between two membranes - plasma (cytoplasmic)

membrane and outer membrane.

Outer membrane contains lipopolysaccharides and lipid A.

Lipid A is a part of endotoxins that is released only from the dead bacterial cells.

Microbes are likely to be resistant to penicillin and are generally less sensitive to

Antibiotics than Gram positive bacteria.

Acid fast Bacteria:
Thick layer of peptidoglycan covered by lipopolysaccharides and layer of hydrophobic

mycolic acids, lipids, and waxy material, which makes the cell wall very hydrophobic. Acid-fast bacteria are slow growing organisms.

9.    [03-05] Why are Gram-positive bacteria generally more sensitive to antibiotics than Gram-negative and Acid-fast bacteria? – Lecture 1, Slide 28 –
Both Gram-negative and Acid-fast bacteria have lipopolysaccharides, which act as a hydrophobic barrier. Gram-negative bacteria have the added bonus of a second outer membrane, while Acid-fast bacteria have the benefit of multilayered protection with LPS and mycolic wax layer.

10. [03-06] Compare bacterial flagella to bacterial pili. Name bacterial species that have flagella. Name bacterial species that have pili but not flagella – Lecture 1, Slide 29 –

Flagella also can participate in bacterial attachment to substratum or host cells. Flagella are attached to plasma (cytoplasmic) membrane via rod. ( E. Coli, B.S., Salmonella enterica) Pilli is shorter and thinner than Flagella. DNA Transfer ( Neisseria Gonorrhoeae and Shigella spp. And Streptococcus pyogenes).

11. [03-07] Describe sporulation of bacteria. Name bacterial groups that can form endospores and those that cannot form endospores – Lecture 1, Slides 33-34 –
 Sporulation – Process of endospore formation.

1)    DNA is replicated – Growth of bacterial cell stops due to limited nutrient supply.

2)    Septum is formed – Separates newly replicated DNA, divides cell asymmetrically.

3)    Forespore is formed – Larger compartment engulfs smaller one forming 2^nd layer of membrane around forespore.

4)    Cortex is formed – Peptidoglycan, dipicolinic acid, and calcium ions deposited between outer and inner membranes.

5)    Spore coat is formed – Spore specific proteins deposited on surface of spore.

6)    Spore is released – When mother cell is degraded.

**Gram negative bacteria DO NOT form endospores, gram positive bacteria DO.

Gram positive spore forming bacteria: (Bacillus, Clostridium)

Gram-positive NON-spore forming bacteria: (Streptococcus pyogenes, Streptomyces)

Gram negative NON-spore forming bacteria: (Vibrio, Salmonella, Pseudomonas)

12. [03-08] Compare the properties of bacterial cell and endospore – Lecture 1, Slide 35 – 

Vegetative bacteria cells are metabolically active, have cell walls, and are undergoing enzymatic activity. Their cell activity makes them sensitive to lysozyme, heat, and radiation. Endospores, on the other hand, have a spore coat and cortex, No metabolic or enzymatic activity, which provides a high resistance to heat, chemicals, and radiation.

13. [03-09] Compare prokaryotic and eukaryotic cells by describing their similarities and differences – Lecture 1, Slide 38 –
Both Prokaryotic and eukaryotic cells are built of proteins, lipids, nucleic acids (RNA and DNA) and have plasma (cytoplasmic) membrane as natural semi-permeable boundary. Both types of cells have 70S ribosomes. Differences: Eukaryotic cells are much bigger than prokaryotic cells. Eukaryotic cells have multiple linear chromosomes arranged in pairs, while prokaryotic cells have single circular chromosome. Eukaryotic cells have nucleus, membrane-bound organelles and 80S ribosomes, while prokaryotic cells have none of them. Prokaryotic cells are going via simple division (binary fission), while eukaryotic cells are going via mitosis or meiosis.

14. [03-10] Consider bacterial cell wall, plasma (cytoplasmic) membrane, and ribosome as targets for treatment of bacterial infections in humans. Which one is the best target and which one is the worst? Explain your answer – Lecture 1, Slides 9, 38 –
Cell wall is best treatment because human cells do not have a cell wall, thereby avoid the risk of human cells being damaged by treatment.