Question

For each of the following determine if its: gram (+),gram(-), both or neither

1. contains teichoic acids

2. contains mitochondria for energy production

3. contain 70s ribosomes

4. loses color when decolorizer applied during gram stain

5. contains peptidoglycan

6. contains a lipopolyaccharide layer

7. contains interbridges (crosslinks)that hold tetrapeptides together

Answer 1

1. Gram Positive ; Wall teichoic acids are found only in certain Gram-positive bacteria (such as staphylococci, streptococci, lactobacilli, and Bacillus spp.) and appear to extend to the surface of the peptidoglycan layer, so far, they have not been found in gram- negative organisms. Wall teichoic acids and their attached substituents contribute to bacterial cell surface charge and hydrophobicity, which in turn affects binding of extracellular molecules. This plays a role in protecting bacteria from various threats and adverse conditions.

2. Gram Negative ; One of the hallmarks of eukaryotic cells is the presence of intracellular organelles. These organelles are defined by limiting membranes, and these organelles perform a number of essential cellular processes. Mitochondria, for example, are organelles that provide eukaryotes with most of their energy by producing energy-rich molecules called ATP. Prokaryotes lack mitochondria and instead produce their ATP on their cell surface membrane. Eukaryotes stain gram negative.

3. Both Gram Positive and gram negative ; Ribosomes are the site for protein synthesis and have two subunit; large and small. Prokaryotic ribosomes have 30S and 50S subunits that together make a 70S ribosome. Both Gram positive and negative bacteria have unit cell membrane of phospholipids and 70S ribosomes.

4. Gram Negative ; Due to differences in the thickness of a peptidoglycan layer in the cell membrane between Gram positive and Gram negative bacteria, Gram positive bacteria (with a thicker peptidoglycan layer) retain crystal violet stain during the decolorization process, while Gram negative bacteria lose the crystal violet stain and are instead stained by the safranin in the final staining process.

5. Both Gram Positive and gram negative ; the peptidoglycan later is present in both gram postive and gram negative bacteria. But the thickness in the cell membrane differ. In the Gram-positive Bacteria, the cell wall is thick (15-80 nanometers), consisting of several layers of peptidoglycan. In the Gram-negative Bacteria the cell wall is relatively thin (10 nanometers) and is composed of a single layer of peptidoglycan surrounded by an outer membrane.

6. Gram negative ; The outer membrane of Gram-negative bacteria invariably contains a unique component, lipopolysaccharide (LPS or endotoxin), which is toxic to animals. In Gram-negative bacteria the outer membrane is usually thought of as part of the cell wall .

7. Gram Positive ; In most gram positive species the tetrapeptide species are cross linked via short peptide interbridge ; is a cross-bridge of five amino acids such as glycine (peptide interbridge) that serves to connect one tetrapeptide to another.