Escherichia Coli

INTRODUCTION

        Escherichia coli is one of the most frequent causes of many common bacterial infections including cholecystitis, bacteraemia, cholangitis, urinary tract infection (UTI), and traveller’s diarrhea and other clinical infections.

        The genus Escherichia is named after Theodor Esherich who isolated the type species of the genus. Escherichia organisms are gram-negative bacilli that exist singly or in pairs. E. coli is facultative anaerobic with type of metabolism that is both fermentative and respiratory. They are either non-motile or motile by peritrichous flagella. E. coli is a major facultative inhabitant of the large intestine.

Escherichia coli METABOLISM

Escherichia coli or as known as E. coli is a heterotrophic organism, meaning that it obtains its food from a different source. This source is most often its host organism and from their host, they will obtain carbon via biosynthesis of organic molecules that were ingested by their host. Carbon is very important to E. coli because the bacterial cell is composed almost entirely of carbon molecules bound to other important elements which are carbohydrate, hydrogen, nitrogen, oxygen, phosphorus and sulphur.

A relative of E. coli has all the heterotrophic capabilities as the ability to grow by photoautotrophic, photoheterotrophic or lithotrophic. It does require one growth factor which biotin must be added to its growth media.

E. coli ‘s main source of carbon comes from glucose molecules ingested by its host organism. This is then broken down into useable carbon by means of central metabolism, which consists of three steps:

• Emben-Meyerhof-Parnas (EMP) Pathway: converts glucose to pyruvate
• Tricarboxylic Acid (TCA) cycle: oxidizes Acetyl CoA to carbon dioxide, CO2
• Pentose Phosphate Cycle (PPP): oxidizes glucose to carbon dioxide, CO2     

[pic 1]

FIGURE 1: Central Metabolism of E. coli

PRODUCTION OF ATP

        E. coli can produce energy for growth by fermentation or respiration. It can respire aerobically using O2 as final acceptor or it can respire under anaerobic conditions which is using NO3 or fumarate as terminal electron acceptor. E. coli can use glucose or lactose as a sole carbon for growth with metabolic ability to transform sugar into all the necessary amino acids, vitamins and nucleotides that make up cells. High ATP production is essential for ensuring the organism will have energy to allow metabolism to occur.