The Prokaryotic Cell

Introduction on prokaryotic organisms

Cyanobacteria (Source)

Introduction

This article is about the prokaryotic cell and its main characteristics. The word prokaryote comes from ancient Greek. The prefix pro- means before and the suffix -karyote means kernel or nucleus. According to Lynn Margulis on her theory of endosymbiosis, eukaryotic organelles arose from an evolution of prokaryotic cells. She saw that they had some properties in common such as being surrounded by a plasma membrane, having a round chromosome or having a similar reproduction process. This is where the small (prokaryotes) benefit the big (eukaryotes) in exchange for “a place to live”.

Lynn Margulis (Source)

Main Characteristics

• Prokaryotic cells do not have membranous structures.
• Lack organelles with membranes (e.g mitochondria, chloroplasts, etc)
• Their size ranges from 3 to 30 micrometres (normally)
• They are surrounded by a plasma membrane and a cell wall which can be targeted by bacteriophages using the enzyme endolysin.
• They have one round chromosome (generally)

Classes of Prokaryotic Organisms

• Archaebacteria
  They are the oldest type of prokaryotic organisms. They live in very extreme conditions, that’s why, they are also called extremophiles.
• Cyanobacteria
  They are primitive bacteria capable of carrying out photosynthesis resulting in one of the first autotrophic organisms. Thanks to them, we have an oxygen rich atmosphere. They produce toxic waste, cyanotoxins, that are harmful to humans and animals.
• Bacteria
  These organisms live in nearly any place on earth. They can be autotrophic and heterotrophic. They are classified according to their shape: cocci, bacilli, spirilla & vibrio. For more information, check out either of these two videos: Spanish Video, English Video.

Electron Micrograph of E. Coli (Source)

Structure

List of prokaryotic cell structures:

• Flagellum (not always present): Aids cellular locomotion. Made up of cytoskeletal proteins.
• Cell Membrane: It is made up of lipids. It controls which substances can get in and out of the cell. It surrounds the cytoplasm.
• Cell Wall (mostly present): Protects the bacteria and gives it a shape. It is made up of peptidoglycan. It is targeted by many antibacterials.
• Ribosome: Organelle in charge of producing proteins.
• Nucleoid: This is the area of the cytoplasm where the genetic material is.

How can we use prokaryotes for our own benefit?

The food industry heavily depends on bacteria. Nestle, for example, has its own patented bacteria for making its yogurts (Source). Cyanobacteria, according to its Wikipedia website, can be used for producing dietary supplements, bioethanol and raw materials. To finish, archaebacteria are extremely useful for extracting heat resistant enzymes that have been used for PCRs and low lactose milk, just to list a few. They also provide a completely new type of potentially useful antibiotics and are a vital part of sewage treatment.

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