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Bacterial Cell Wall and Envelopes
Study
What are the essential components of the bacterial cell?
The essential components of the bacterial cell are the cell wall, cytoplasmic membrane, and the cytoplasm.
What is the structure of the bacterial cell wall?
The cell wall is the outermost component in all bacteria, except mycoplasma, and is composed of a peptidoglycan layer.
What is the function of the peptidoglycan in the cell wall?
1. It provides rigid support for the cell and is important in maintaining the characteristic shape of the cell. 2. It is a good target for antibacterial drugs such as penicillins, cephalosporins, and vancomycin because of its absence in human cells.
What are the components of the cell wall in Gram-positive bacteria?
1. The peptidoglycan layer, which is thick and forms about 50 to 80% of the cell wall materials. 2. Fibers of teichoic acid that protrude outside the peptidoglycan and are highly immunogenic antigens.
What are the components of the cell wall in Gram-negative bacteria?
1. The peptidoglycan layer, which is very thin and forms 5-10% of the cell wall materials, lying in the periplasmic space and maintained by lipoprotein molecules. 2. Outer membrane, which is a bilayered structure with an inner layer composed of phospholipids and an outer layer composed of lipopolysaccharides.
What is the composition of Gram-positive bacteria cell wall?
1. The peptidoglycan layer (thick, forming about 50-80% of the cell wall materials) 2. Fibers of teichoic acid that protrude outside the peptidoglycan and are highly immunogenic antigens
What is the composition of Gram-negative bacteria cell wall?
1. The peptidoglycan layer (very thin, forming 5-10% of the cell wall materials) 2. Outer membrane (bilayered structure with inner layer composed of phospholipid and outer layer composed of lipopolysaccharide (LPS) 3. Periplasmic space (filled with gel, lying between the outer membrane layer and the cytoplasmic membrane)
What are the functions of the cell wall in addition to the function of peptidoglycan?
Additional functions of the cell wall include maintaining stability by lipoprotein molecules, providing structural components unique to Gram-negative outer membrane (e.g., LPS), and separating the cytoplasmic membrane from the external environment.
What is the space lying between the outer membrane layer and the cytoplasmic membrane filled with gel?
Periplasm
What are the functions of the cell wall in addition to the function of peptidoglycan?
1. It plays a role in cell division 2. It acts as a channel to allow the entry of essential substances, such as sugars, amino acids, vitamins, and metals, as well as many antimicrobial drugs. 3. It plays an important role in determining the reaction to Gram stain.
Bacterial Size, Shape, Arrangement, Staining Properties, and Motility
Study
What are the two fundamentally different types of cells?
Eukaryotic and prokaryotic cells
How can eukaryotic and prokaryotic cells be distinguished?
On the basis of their structure and complexity of organization
What distinguishes fungi from bacteria in terms of cell type?
Fungi are eukaryotic, whereas bacteria are prokaryotic
What are the characteristics of eukaryotic human cells and prokaryotic bacterial cells?
1. Eukaryotic human cells have a cell wall containing peptidoglycan, while prokaryotic bacterial cells have a cell wall with no peptidoglycan except Mycoplasma. 2. Eukaryotic human cells have sterol in the cytoplasmic membrane, while prokaryotic bacterial cells do not, except Mycoplasma. 3. Eukaryotic human cells have organelles such as mitochondria and lysosomes, while prokaryotic bacterial cells have no organelles. 4. Eukaryotic human cells have a nucleus, nuclear membrane, and more than one linear chromosome, while prokaryotic bacterial cells have no nucleus, nuclear membrane, and one circular chromosome. 5. Eukaryotic human cells have 80S ribosomes, while prokaryotic bacterial cells have 70S ribosomes.
What is the nomenclature of bacteria?
The phylum of bacteria is family, genus, species, and type or strain.
What are the morphological characters of bacteria?
The morphological characters of bacteria include size, shape, arrangement, staining properties, and motility.
What is the size range of bacteria?
Bacteria range in size from about 0.125 to 5 micrometers.
How are bacteria classified by shape?
Bacteria are classified by shape into three basic groups: cocci, bacilli, and spiral. Some bacteria are variable in shape (pleomorphic).
Why is the arrangement of bacteria important?
The arrangement of bacteria is important for classification and identification.
What is the size range of bacteria?
Bacteria range in size from about 0.125 to 5 micrometers (m).
How are bacteria classified based on shape and arrangement?
Bacteria are classified into three basic groups: cocci, bacilli, and spiral. Some bacteria can also be pleomorphic, meaning they are variable in shape.
What are the two groups of bacteria based on their staining properties?
According to Gram stain, bacteria are divided into two groups: Gram-positive bacteria and Gram-negative bacteria.
What are negative bacteria?
Negative bacteria are a group of bacteria that have a cell wall composed of a thin layer of peptidoglycan surrounded by an outer membrane of lipopolysaccharides.
Give an example of a negative bacteria.
Escherichia coli (E. coli) is an example of a negative bacteria.
How do negative bacteria differ from positive bacteria?
Negative bacteria have a more complex cell wall structure with an outer membrane, while positive bacteria have a simpler cell wall structure without an outer membrane.
General Bacteriology
Study
What is microbiology?
Microbiology is the science of minute organisms invisible to the naked eye, named microbes.
What are the subdivisions of medical microbiology?
Bacteriology, Virology, and Mycology.
What is bacteriology?
Bacteriology is the science of bacteria, the causative agents of a number of infectious diseases.
What is virology?
Virology is the science of viruses, non-cellular living agents capable of causing infectious diseases in man.
What is mycology?
Mycology is the study of fungi pathogenic for man.
