Introduction

​

Nutrition is a process by which nutrients are acquired from the environment and used in cellular activities such as metabolism and growth. Microorganisms require certain nutrients for growth and maintenance of metabolic functions. The amount and type of nutrients required range widely depending on the microorganism. Microorganisms are the most versatile and diversified with regard to their nutritional requirements. Some microbes have an unconditional need for performed complex organic compounds while others can thrive with just few inorganic substances as their sole nutritional requirements.

       Microorganisms can derive energy form carbohydrates, alcohols and amino acids. Some of them can use fat as an energy source. 

       Although great variation is found in the specific requirements for for growth of diverse species of microorganisms, in general, the nature and functions, of growth substances are common for all cells. This is because the chemical composition of microbial cells is more or less similar. Analysis of microbial cell composition show that over 95% of cell dry is madre up for a few major elements:

• Carbon

• Hydrogen

• Oxygen

• Nitrogen

• Sulfur

• Phosphorus

• Potassium

• Calcium

• Magnesium 

• Iron 

These​ are called macroelements or macronutrients because they are required by microorganisms in relatively large amounts. The first 6 elements (C, H, O, N, S and P) are components of:

• Carbohydrates

• Lipids

• Proteins

• Nucleic acids.

The remaining four (K, Ca, Mg and Fe) plays a variety of roles as cations in the cell wall.

       All organisms, including microorganisms, require several micronutrients or trace elements (Zn, Mn, Co, Mo, Ni and Cu). Cells require such a small amounts that contaminants in water, glassware and regular media components often are adequate for growth. Micronutrients are normally a part of enzymes and cofactors, and the aid in the catalysis of reactions and maintance of protein structure. 

      Assimilated nutrients need to be metabolized. Some microorganisms use nutrients absorbed by the cell as the source of energy (catabolism), which is the reverse of biosynthesis (anabolism). Other microorganisms derive their energy from the trapping of light and also convert it into chemical energy. This energy is then hamessed to do work for the cell. 

​

Sources of Nutrients (Macroelements)

​

Carbon

This is the most importan element required for microbial growth. Carbon forms the backbone of three major important nutrients: carbohydrates, lipids and protein, these compounds provide energy for cell growth and serve as building blocks of cell material.

    Although a distinction is made between the type of carbon compound cells absorb as nutrients (inorganic or organic), the majority of carbon compounds involved in the normal structure and metabolism of a cells are organic.

​

Nitrogen

All microorganisms require nitrogen in some form, this element is needed for the structure of proteins, DNA, RNA and ATP. Such nitrogenous compounds are the primary nitrogen source for heterotrophs, but to be useful, they must be first be degraded into their basic building blocks (proteins into amino acids; nucleic acids into nucleotids).

   Many prokaryotes use inorganic nitrogen compounds such as nitrates, nitrites, or ammonium salts. Some microorganisms use nitrate as an alternative electron acceptor in electron transport.

​

Oxygen

Is a major component of organic compounds such as carbohydrates, lipids, nucleic acids, and proteins, it plays and important role in the structural and enzymatic function of the cell. 

      Free oxygen (O2) makes up 20% of the atmosphere, which is toxic to most strict anaerobic bacteria and some archaeons, although aerobic microorganisms use oxygen as a terminal electron acceptor in aerobic respiration.

​

Hydrogen

Hydrogen is a major element in all organic and several compounds, it performs these overlapping roles in the biochemistry of cells: 

• Maintaining pH

• Forming hydrogen bonds between molecules, and

• Serving as the source of free energy in oxidation reduction reactions of respiration.

​

Phosphorus

The main source of phosphorus is phosphate, derived form phosphoric acid. Phosphate is a key component of nucleic acids and is therefore essential to the genetics of cells and viruses. 

      It is a component of teichoic acids and teichuronic acids in the cell wall of Gram-positive bacteria, as well as a component of various membrane phospholipids. Becuase is also found in ATP, also serves in cellular energy transfers.

​

Sulfur

Most microorganisms use sulfate as a source of sulfur and reduce it by assimilatory sulfate reduction. Sulfur is an essential component of some vitamins (vitamin B1) and the aminoacids methionine and cysteine; the latter help determinate shape and structural stability of proteins by forming unique link-age called disulfide bonds.

​

​

Mineral irons (Macroelements)

​

Potassium

Is essential to protein synthesis and membrane function.

​

Calcium

Is an stabilizer of the cell wall and endospores of bacteria.

​

Magnesium

Serves as a cofactor for many enzymes, complexes with ATP, and stabilizes ribosomes and cell membranes. Is a component of cholorphyll.

​

Iron

Is a part of cytochromes and a cofactor for enzymes and electron-carrying proteins.

​

Other Nutrients (Microelements)

​

Zinc

Is present at the active site of some enzymes​. It is a major component of "zinc fingers"-binding factors that enzymes adhere to specific sites on DNA.

​

Coper

Is a component of vitamin B12

​

Manganese

Aids many enzymes catalyzing the transfer of phosphate groups.

​

Molybdenum

Is required for nitrogen fixation.

​

​

​