The science of microscopic organisms(fungi)

FUNGI

Mycology, a branch of biology deals with the study of fungi. Fungi are group of eukaryotic, heterotrophic organisms. They are dependent on organic compounds for their nutrition. In general, fungi can withstand extreme environmental conditions better than most of the microorganisms.

CHARACTERISTICS OF FUNGI

Fungi cells are usually larger than the bacteria. The sizes may range 1-5 µm in width and 5-35 µm in length. Fungal cells may be elongated or spherical.

The fungi are heterotrophic, since they cannot synthesize their own food from the inorganic compounds

IMPORTANCE OF FUNGI

As is the case with bacteria, fungi are both friends and enemies of humans.

BENEFICIAL ASPECTS OF FUNGI

The yeasts are useful for the following 

• Alcohol fermentation e.g. Saccharomyces cerevisiae.
• Production of Vitamins e.g. Ashbya gossypii.
• Citric acid fermentation e.g. candida sp.
• Baker's Yeast e.g. S. cerevisiae.

The application of molds are listed

• Production of enzymes e.g. Aspergillus sp.
• Citric acid fermentation e.g. Aspergillus niger.
• Penicillin production e.g. Penicillium notatum.
• Steroid transformation e.g. Rhizopus sp.
• Gluconic acid production e.g. Aspergillus niger.

HARMFUL ASPECTS OF FUNGI

• Spoilage of foods e.g. moldy bread, rot of fruits and vegetables
  
  
  • Deterioration of textiles made up of cotton.
  • Damage to paper.
  • Diseases caused by fungi. e.g. ringworm of the scalp in children caused by Microsporum audouinii.

   

  CONTROL OF FUNGI 

  The fungal growth can be controlled by using phenol and its derivatives e.g. cresol, ethylphenol, propylphenol, butylphenol. Chlorine and chlorine compunds are also useful in this regard.
  
  
  Vegetative cells of yeasts and other fungi can be destroyed by moist heat at 50-60˚ C for about 5-10 minutes. Spores, however require higher temperature 20-80˚ C.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  
  

    

 

The science of Microscopic organisms

MICRO ORGANISMS

Microbiology (Greek , mikros- small ; bios- life) is the science of small or microscopic organisms. The most important microorganisms relevant to biotechnology include bacteria, fungi , and viruses.

Microorganisms are very widely distributed , and are almost found everywhere in nature. In general, the conditions for their growth and , multiplication (food, temperature, moisture etc.) are similar to that of humans. Hence, they are most abundantly present at places where people live. 

Here is the brief description of the microorganisms, relevant to biotechnology.

BACTERIA

Bacteriology, the study of bacteria, forms a major part of microbiology. The population of bacteria exceeds all other organisms. 

For instance, 1 kg of a soil may contain more bacteria than the entire population !

Bacteria are very important in biotechnology for the following reasons;

1. Diseases they cause 
2. Domestic uses
3. Industrial applications
4. Agricultural processes

CHARACTERISTICS OF BACTERIA

     Bacteria are prokaryotic unicellular organisms. They lack organized nucleus, but possess a rigid cell wall comparable to that found in plants. The average size of a bacterium is around 2

µm. The bacteria may be spherical , rod-like, spirally coiled or filament like. certain bacteria may occur in more than one form.

GRAM POSITIVE AND GRAM NEGATIVE BACTERIA

Based on the response to Gram's stain, the bacteria are grouped as Gram +ve or Gram -ve. By Gram's stain several distinguishing features of bacteria can be identified. For instance, Gram +ve bacteria possess single-layered cell wall while Gram -ve bacteria have a double- layered one.

AEROBIC, ANAEROBIC AND FACULTATIVE BACTERIA

On the basis of respiration (i.e. response to O₂), the bacteria are grouped into three categories

1. Aerobic bacteria : These bacteria require oxygen for their growth e.g. Pseudomonas sp, Mycobacterium sp.
2. Anaerobic bacteria: They do not require O₂ to obtain energy, and to grow. In fact, the presence of  O₂ is toxic to them e.g. Peptococcus sp.
3. Facultative bacteria : The bacteria that can grow in both aerobic and anaerobic conditions are regarded as facultative bacteria. e.g. Shigella sp, Salmonella sp.

NUTRITIONAL ASPECTS OF BACTERIA

Based on their nutrition , the bacteria are categorized as autotrophic or heterotrophic.

AUTOTROPHIC BACTERIA

1.  Autotrophic bacteria: These bacteria are capable of  synthesizing their own food from inorganic substances. They are comparable to higher plants in this aspect. They utilize different hydrogen compounds ( not H₂ O as in the case of higher plants). These include hydrogen, ammonia, hydrogen sulfide and methane e.g. Hydrogenomonas sp, Nitrosomonas sp, Methanomonas sp.
2.  Heterotrophic bacteria : These bacteria cannot synthesize their own food and are therefore dependent on the outside source. Heterotrophs are of two types- sporophytes and parasites.

•  Sporophytes obtain their food frpm sources of animal or plant origin. These include organic remains like corpses, animal excreta, meats, fruits and various other products of plant and animal origin. They secrete digestive enzymes that break the complex organic molecules into simpler and easily absorbable forms. These heterotrophic bacteria are useful for the disposal of sewage , cleansing of leather, and manufacture of certain compounds ( alcohol, organic acids). Sporophytes can also spoil foods, and damage soils (by denitrification).
• Parasites are the bacteria that obtain their food from living organisms, namely the hosts. They may be either harmless (non-pathogenic) or harmful (pathogenic) to the hosts. E.coli is a good example of non-pathogenic bacteria which has a symbiotic relationship in the human intestine. The pathogenic bacteria may cause serious diseases either by destroying the host's cells or releasing toxins e.g. Clostridium tetani.

IMPORTANCE OF BACTERIA 

         Bacteria play a very important and crucial role in the continuous sustenance of life on earth. They are both friends and enemies of humans. Bacteria are more important due to the diseases they cause, industrial and agricultural applications.