Microbiology - Ampersand Tutorials

Culture Media Composition – Easy Read in 2 min

02/11/2021

by Vijay Gladwin with No Comment Microbiology

to know in detail about culture media composition used in the field of microbiology

Culture Media

Microorganisms, like other living organisms, require necessary nutrients for the growth and sustenance of life. The food materials on which microbes are grown artificially in a lab is known as culture media.

Media is an environment provided artificially in a lab supplying the required nutrients for the growth of the microorganism.

History

The first person to identify a culture media was Lazaro Spallanzani, and later it was Robert Koch who has developed the same.

Koch first used a cut, half-boiled potato as a base to grow the microbes. Soon, he discovered that the base of the potato, eaten away, then he started using Gelatin.

Gelatin was also not successful as it had a melting point of 21ºC and on incubation gelatin became liquid. Later Mrs Hesse, wife of an associate of Robert Koch, suggested the use of agar which she was suing in her jams and jellies.

The discovery of Agar was a turning point in the history of culture media composition.

Composition of culture media

Different types of culture media composition are identified to isolate, grow and identify them. Different culture media compositions are prepared depending on the nutrient requirement of the microbes.

The essential ingredients of a culture media are as follows

Carbohydrates

Simple and complex sugars are used as a source of carbon and energy.

Examples: Glucose, Lactose, Sucrose

Peptone

Peptone is a source of nitrogen and minerals. It is a water-soluble product obtained from the breakdown of animal or plant protein, and it is a mixture of peptides and amino acids.

Examples: Meat, Soya Bean

Meat Extract

Meat Extract is an aqueous meat infusion made by soaking fresh beef in water and provides the organism with a further supply of vitamins, minerals, sulphates, sulphides essential for the growth of the organism.

Yeast Extract

Yeast Extract is an autolysate made from yeast cells, and it is a common ingredient of culture media due to the presence of the B complex.

Mineral salts

Salts of Sulphur, Magnesium, Phosphorous are used in the media for enzymatic functions.

Agar-Agar

Corneum geladium is a polysaccharide extracted from seaweed, algae belonging to the family Rhodhophyceae, and it contains two main polysaccharides agarose (70-75%) and agar protein (20-25%).

Agar-agar is used as a solidifying agent in the media agent in the media preparation, giving a solid surface for the growth of microorganisms.

Its unique property is that it sets below 40ºC and melts at 90-95ºC. Besides, not attacked by the microbes as it is not a nutrient.

Water

Water is essential as it helps to dissolve all ingredients used for the preparation of the media. Deionized or distilled water is safe to use in the culture media as it is free from the inhibitory effect of chemicals.

For more details about various courses, check out Ampersand Academy.

3 Types of Nutrients and Media – Learn Easy

01/11/2021

by Vijay Gladwin with No Comment Microbiology

know about the details of nutrients and media types such as macronutrients and micronutrients

Nutrients and Media

The substances from which the microbes synthesise new cellular materials and obtain energy are called nutrients.

These nutrients must be supplied as utilisable compounds that take part in the synthesis of new cellular compounds.

Types of Nutrients

The three different types of nutrients are as follows

Macronutrients
Micronutrients
Trace elements

Macronutrients

Macronutrients are nutrients required in relatively large quantities. Macronutrients are the primary building blocks molecules for the growth of microbes and play an essential role in cell structure and metabolism and are weighed in grams per litre.

The significant macronutrients are Carbon (C), Nitrogen (N), Sulphur (S) and Phosphorus (P).

Carbon Source

Carbon source forms the basic skeleton for all organic molecules. These carbon-containing compounds are the energy source to synthesise new cellular components.

The different types of carbohydrates used are Glucose, Fructose and Starch.

Nitrogen Source

Nitrogen is the major component of amino acids and proteins and uses nitrogen to synthesise various enzymes. Nitrogen is the source present in nutrients and media to provide nutrition like protein.

When hydrolysed by enzymes, it breaks down into peptides and then into amino acids.

Peptone is a standard universal ingredient used as a nitrogen source in the preparation of all media.

Sulphur Source

Sulphur is the main constituent present in nutrients and media of many sulphur-containing amino acids like Cysteine, Methionine.

Microbes use sulphur to make the components of coenzymes.

Phosphorus Source

Microbes obtain phosphates to synthesise PO₄ ions to prepare teichoic acids, ATP, phospholipids, nucleic acids. ATP is an essential source of energy. Microbes accumulate PO₄granules in the form of metachromatic granules found in Corynebacterium diphtheriae.

Micronutrients

Micronutrients are present in nutrients and media required in relatively smaller quantities when compared to macronutrients.

They are the minor components of building block materials but are still essential for the growth of the microbes and are generally weighed in milligrams per litre.

The significant micronutrients are Potassium (K), Calcium (Ca), Magnesium (Mg), Iron (Fe).

Potassium

Potassium is the principal source present in nutrients and media to provide inorganic cation in the cell and is required for ribosomes and enzymatic functions and the cofactors for some enzymes.

Calcium

Calcium acts as a cofactor acting as the cellular cation. During unfavourable conditions, it helps to form heat resistant spores. Calcium is deposited in the form of DPA.

Magnesium

Magnesium acts as an essential cellular cation, serving as a cofactor for many enzymatic functions, binding enzymes to the substrates and forming an Mg complex with ATP.

Iron

Iron is a vital constituent of cytochromes and other proteins and serves as a cofactor for many enzymatic functions. It is available to the cell in the form of siderophores.

Trace Elements

The nutrients and media which are used in tiny traces are trace elements and serve as a cofactor for many enzymatic functions. Generally, weighed in micrograms per litre.

The significant trace elements are Zinc (Zn), Molybdenum (Mo), Cobalt (Co), Manganese (Mg), Nickel (Ni).

Zinc

Zinc is used by the microbial cell for DNA & RNA polymerase enzymatic functions. It also helps in producing essential metabolites.

Molybdenum

Molybdenum is an essential component of Ferredoxin in the Nitrogenase enzyme present in all nitrogen-fixing bacteria. (Rhizobium)

Cobalt

Cobalt is an essential vital component of the Vitamin B₁₂ molecule.

Manganese

Manganese serves as an alternate capacity for Magnesium deficiency. Many soil bacteria reduce Mn⁺⁴ to Mn⁺² and are also used in the synthesis of metabolites like antibiotics.

Nickel

Nickel is a cofactor for many enzymes.

For more details about various courses, check out Ampersand Academy.

types of nutrition adopted by microorganisms

7 Basic Nutrition Adopted By Microorganisms – Learn Easy

28/10/2021

by Vijay Gladwin with No Comment Microbiology

In this tutorial we learn about the types of nutrition adopted by microorganisms such as heterotrophs, mixotrophs, auxotrophs, protoautotroph, pathogens and symbionts

Heterotrophs

Heterotrophs are a Nutrition adopted by microorganisms that cannot synthesise their food using inorganic sources like carbon dioxide and their dependence upon complex organic substances as a source of carbon are called Heterotrophs. 95% of all living organisms are heterotrophs including animals, fungi and most bacteria, called consumers.

Heterotrophs are those that break down complex organic compounds such as carbohydrates, fats and protein produced by autotrophs into simpler compounds, carbohydrates to glucose, fats to fatty acids and glycerol and proteins into amino acids.

Nutrition adopted by microorganisms that specifically feed on the dead and decayed organic matter is called Saprophytes and release energy by oxidising carbon and hydrogen atoms present in these organic compounds to carbon dioxide and water respectively.

Organotrophs

An organotroph is nutrition adopted by microorganisms that use organic compounds as electron donors. Organotrophs are heterotrophs using organic compounds as sources of electrons and carbon and use the chemical bonds in the organic compounds as an energy source. These organic compounds include carbohydrates, fatty acids, alcohols.

Example: Rhodospirillum uses fatty acids to derive energy, purple non-Sulphur bacteria organotrophic bacteria.

Mixotrophs

A Mixotroph is a nutrition adopted by microorganisms that can utilise a mixture of various sources of energy and carbon, as a replacement for having a single trophic mode of autotrophy at one end to heterotrophy at the other.

Mixotrophs can be either eukaryotic or prokaryotic and can take advantage of different environmental conditions. Mixotrophs can either be obligate or facultative, and the combination can be photo and chemotrophy, litho and organotrophy or auto and heterotrophy.

Example: Beggiota sp

Auxotroph

An auxotroph (Auxo means to increase nourishment) of an organism is defined as the inability of the organism to synthesise a particular organic compound required for its growth. For example, E.coli cannot grow until histidine, supplied in the media.

Auxotrophy results from a cell’s genetically determined inability to produce a reasonable amount of functional enzymes catalyse the synthesis of essential growth factors. Replica plating techniques is an essential method for the isolation of auxotrophic mutants.

Protoautotroph

Protoautotroph is one type of nutrition adopted by microorganisms that can synthesise all the compounds required for its growth, that parent organism could and requires minimal culture media that lacks even certain growth factors. E.coli can thrive and synthesise all its cell components in a solution containing several minerals and glucose as a source of energy and carbon. Protoautotrophs are precisely opposite to auxotrophs.

Pathogens

Pathogens (Pathos means Suffering) or Parasites are nutrition adopted by microorganisms that cause suffering or disease in other living organisms and are heterotrophs that depend on other organisms for their nutrients and multiplication and benefit themselves by causing harm to the host cell and the organism that harbours the parasites called as a host.

Examples: Mycobacterium tuberculosis causing disease in humans and Xanthomonas oryzae, causing bacterial blight in paddy plants.

Symbionts

Symbionts mean together, organisms that live in association with other organisms for food and shelter. This symbiotic relationship where both participating symbionts benefit from each other is now referred to as mutualism.

Symbionts in mutualism are often interdependent—the interaction between Rhizobia species and the plant legumes. The symbiont Rhizobia fix atmospheric nitrogen to a readily available nitrogen source for use by the legume.

In return, legume provides Rhizobia with specific metabolites (Malate and Succinate) through the process of photosynthesis.

Example: Rhizobium and Leguminous plants.

For more details about various courses check out Ampersand Academy

Autotrophs are Manufacturers of Food

26/10/2021

by Vijay Gladwin with No Comment Microbiology

Autotrophs are Manufacturers of Food

An Autotroph – “ Self-Feeding”, from the Greek autos “Self” and trope “Nourishing”, is an organism that fabricates complex organic compounds such as carbohydrates, fats, and proteins from simple substances present in its surroundings. In short, they are the producer organisms that can make their food by photosynthesis or chemosynthesis and occupy the first trophic level.

Photoautotrophs – Manufacturers of Food by Photosynthesis

Photoautotrophs are autotrophic organisms that carry out photosynthesis using energy from sunlight, carbon dioxide as terminal electron acceptor and water, converted into organic materials used in cellular functions such as biosynthesis and respiration. There are fabricators in a food chain like plants on land and algae on the water (Eukaryotes). In the case of Prokaryotes, Purple Sulphur bacteria and Cyanobacteria are photoautotrophic prokaryotes.

Chemotrophs – Manufacturers of Food by chemosynthesis

Chemotrophs are organisms that make their food by chemosynthesis. It is a process that synthesises organic compounds from carbon dioxide using chemical energy by utilising inorganic compounds like hydrogen sulphide, sulphur, ammonium and ferrous iron as reducing agents found in hostile environments like deep-sea vents, where light cannot easily penetrate.

Examples: Methanogens, Halophiles, Nitrifiers, Thermoacidophiles

Lithotrophs

Lithotrophs are consumers of rocks. They are autotrophs that use an inorganic substrate of mineral origin as reducing agents or electron donors for the biosynthesis of organic compounds. Hence they are also called Chemolithotrophs. They produce a particular toxin that dissolves the minerals present in the rocks.

Examples: Purple sulphur bacteria, Nitrifying bacteria, and Hydrogen oxidisers.

Also, check out our post about Saprophytes.

Saprophytes as Biocontrol Agents

25/10/2021

by Vijay Gladwin with No Comment Microbiology

In this tutorial, you’ll learn about Saprophytes as Biocontrol Agents

Saprophytes

Saprophytes are organisms that develop on the dead and rotting natural issue and do not make any infections plants or creatures. Fungi are an ideal case of saprophytes. The expansion of saprophytes is a deep-rooted act of controlling plant pathogens. This procedure is a proficient biological control, rehearsed since days of yore. Expansion of these saprophytes to the yields likewise upgrades the harvest generation by giving numerous supplements and by counteracting plant pathogens. In contrast to synthetic compounds, used to control pathogens, these saprophytes have pulled in the consideration due to the accompanying elements:

• As they do not bring on any ailment

• Also, increment the creation of the yield

• Prevents numerous maladies which cause devastation

• Increases the capacity of the plants to oppose the sicknesses

• Less natural dangers

Saprophytes as Biocontrol Agents Methods

Antagonism
- Competition
- Use of predative microbes
- Parasitic fungi on plant pathogens
  - Mycoparasitism
  - Mycophagy
  - Nematophagy
  - Mycoviruses