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What are Nucleosides, Nucleic Acid, Nucleotides

“Nucleic acid” is found within the name of DNA (Deoxyribose nucleic acid) and RNA (Ribose nucleic acid), but aren’t DNA & RNA made up of nucleotides? Read on…

Viruses, Viroids, and Prions


Viruses, viroids, and prions are all acellular pathogens. They are not within any kingdom and carry their own significant characteristics.

  1. obligate intracellular parasite – require a host to cause damage
  2. filterable – small enough to be filtrated
  3. contains an outer protein coat and inner genome
  4. has only 1 kind of nucleic acid (RNA or DNA, but never both)
  5. lacks metabolic abilities

Viruses can be found either inside a cell (intracellular) or outside of a cell (extracellular). If it is found extracellular, the virus is called a virion. A virion contains a protein coating called a capsid, which surrounds the core of the virus containing the nucleic acid (either DNA or RNA).  Together with the capsid and the DNA or RNA core is called a nucleocapsid.  Some virions also contain an envelope which is made up of a phospholipid membrane. Both the capsid and the envelope are important in protection and providing shape to the virus.

Read on…

Recombinant DNA technology

Recombinant DNA technology entails modifying the genomes of organisms.

Things needed:

mutagen – anything physical or chemical that causes mutations in an organism

reverse transcriptase – these enzymes were discovered from retrovirses and its effects on DNA. Using reverse transcriptase, scientists are able to make DNA out of RNA.  These DNA are called complementary DNA or cDNA. After making cDNA from eukaryotic mRNA, scientists are able to input cDNA into the genome of the prokaryotic DNA. One main reason why this is useful is that prokaryotes are not able to excise or remove the introns (junk DNA or noncoding sequences) of DNA in eukaryotes. Since eukaryotes mRNA are already processed and had removed the introns, the newly made cDNA would also be free from introns!

Read on…

DNA Organization in Prokaryotes and Eukaryotes

Quick DNA Overview

Double helix deoxyribosenucleic acid

Deoxyribosenucleic acid, as you know in humans and in other eukaryotic organisms codes our chromosomes and makes us the way we are!

Similarly, in prokaryotes, like bacteria, DNA makes up their genetic code or in other words what they are.  This includes their function and their appearance.

Universally, DNA contains purines (adenosine, guanine) and pyrimidines (cysteine, thymine, uracil (found in RNA)).  These guys are the bases, in which three of it together will code for a codon, that signifies an amino acid. A sequence of these codons assist with making up a peptide chain. As you know, peptides together, after having been rearranged into a 3D structure is a protein.

As you can see in the picture, DNA’s backbone is connected by phosphodiester bonds (I can get into this later and why its called what its called). These bonds help create the phosphate backbone of DNA. Since phosphate groups (PO4) are negatively charged, a chunk of PO4used as the backbone of the DNA will make the DNA a highly negative molecule.

As you already know, DNA is a double helix. The two strands are antiparallel. Basically, DNA strands are replicated from what is called the 5′ (five prime) end to the 3′ end (I’ll break it down in another post).



The bases (T, A, G, C) are connected to each other by weak hydrogen bonds.

Read on…

Differential Staining: Capsule and Spore Staining

Similar to Gram stain, acid fast stain, and flagellar stain, capsule and spore stain are used to differentiate between microbes.


Purpose: Our immune system contains neutrophils and macrophages that fight against foreign bodies or antigens. Capsules, which contains mucoid polysaccharides or polypeptides, protects bacterial cells against our immune system (macrophage and neutrophils). Capsules are also resistant to stains, hence capsule stain techniques are staining around the cell and not the cell wall or membrane directly (different from Gram and Acid fast stains).

Acidic or Negative Stain – used to stain the background

  • Nigrosin
  • Congo Red
  • India Ink

In this first step, there is NO heat fixing because it will cause the cells to shrink, which will give a false reading of a white halo around the cells.  This may cause a misrepresentation of a capsule.

Cytoplasm, basic stain

  • Maneval’s
  • Carbol fuschin

The unstained, halo, seen between the stain in cells are the capsule.

Read on…

Eukaryotic Microorganisms with Lab Samples

Eukaryotic microbes consists of: protists, animals, fungi and plants.

In this post, we will be looking at fungi (mostly molds and yeast), protozoan, and helminths.

Fungi are organized into two categories:

Ascomycotina (sac-like fungi such as penicillium, aspergillus, yeast) and zygomycotina (molds such as rhizopus stolonifer) Read on…

DNA Fingerprinting with Example Lab Data

There are various ways in assessing DNA and its components. One widely used is electrophoresis, which utilizes electricity to measure the length of DNA fragments. This mechanism can be used for identification either for unknown diseases or human DNA, determining an inherited disease or finding cures for such diseases (National Health Museum).

What is Electrophoresis?

How is DNA assessed? Read on…

Overview of Metabolism

Read on…

Eukaryotic Cells compared to Prokaryotic Cells

The differences between eukaryotes and prokaryotes are described within the last two former posts. The following table is a reflection and minor edited table found on Pg. 87 of Microbiology with Diseases by Taxonomy, 2nd edition, by Robert Bauman., in Table 3.4 and 3.5. Read on…

Prokaryotic Cell Arrangements & Anatomy: emphasis on Cell Wall

Prokaryotes, as mentioned earlier are cells containing NO nucleus. I will write a post on the major differences of prokaryotes and eukaryotes later.

In microbiology, there are plenty of research under bacteriology (study of bacteria). In this post, we will focus on bacteria (which is made up of eubacteria & archaebacteria).

Relative size of bacteria (measured in micrometer µm) Read on…