gram-positive

Examples of gram-positive in the following topics:

• Basic Structures of Prokaryotic Cells

  • Bacteria are divided into two major groups: gram-positive and gram-negative, based on their reaction to gram staining.
  • Gram-positive organisms typically lack the outer membrane found in gram-negative organisms .
  • Bacteria are divided into two major groups: gram-positive and gram-negative.
  • Both groups have a cell wall composed of peptidoglycan: in gram-positive bacteria, the wall is thick, whereas in gram-negative bacteria, the wall is thin.
  • In gram-positive bacteria, lipoteichoic acid anchors the cell wall to the cell membrane.

• The Origins of Archaea and Bacteria

  • Archaea are believed to have evolved from gram-positive bacteria and can occupy more extreme environments.
  • Within prokaryotes, archaeal cell structure is most similar to that of gram-positive bacteria, largely because both have a single lipid bilayer and usually contain a thick sacculus of varying chemical composition.
  • In phylogenetic trees based upon different gene/protein sequences of prokaryotic homologs, the archaeal homologs are more closely related to those of Gram-positive bacteria.
  • Archaea and gram-positive bacteria also share conserved indels in a number of important proteins, such as Hsp70 and glutamine synthetase.
  • It has been proposed that the archaea evolved from gram-positive bacteria in response to antibiotic selection pressure.

• Endosymbiotic Theory and the Evolution of Eukaryotes

  • More recent work proposes that gram-negative bacteria, which are unique within their domain in that they contain two lipid bilayer membranes, did result from an endosymbiotic fusion of archaeal and bacterial species .
  • More controversial is the proposal that (a) the eukaryotic nucleus resulted from the fusion of archaeal and bacterial genomes; and that (b) Gram-negative bacteria, which have two membranes, resulted from the fusion of Archaea and Gram-positive bacteria, each of which has a single membrane.

• Concept of Osmolality and Milliequivalent

  • One mole is defined as the molecular weight of the solute in grams.
  • For example, the molecular weight of sodium chloride is 58.44; thus, one mole of sodium chloride weighs 58.44 grams.

• Water’s High Heat Capacity

  • Specific heat is defined as the amount of heat one gram of a substance must absorb or lose to change its temperature by one degree Celsius.

• Productivity within Trophic Levels

  • For example, in the English Channel ecosystem, the primary producers account for a biomass of 4 g/m2 (grams per meter squared), while the primary consumers exhibit a biomass of 21 g/m2.

• Water’s Heat of Vaporization

  • As a result of the network of hydrogen bonding present between water molecules, a high input of energy is required to transform one gram of liquid water into water vapor, an energy requirement called the heat of vaporization.

• Importance of Carbohydrates

  • Calorie-wise, a gram of carbohydrate provides 4.3 Kcal.

• History of Bacterial Diseases

  • The causative agent, the (b) bacterium Yersinia pestis, is a gram-negative, rod-shaped bacterium from the class Gamma Proteobacteria.
  • Salmonella enterica serovar typhi, the causative agent of typhoid fever, is a gram-negative, rod-shaped gamma protobacterium.

• Food Requirements and Essential Nutrients

  • Fatty foods are also significant sources of energy because one gram of fat contains nine calories.