Microbial Nutrition -requirements and modes of nutrition

    Microbial cells are structurally complex and carry out numerous functions. Nutrients are required for microbial growth to support biosynthesis and energy release. Microorganisms use nutrients and a source of energy to construct new cellular components and do cellular work.

Common Nutrient Requirements

Macroelements/Macronutrients : Macro elements or macronutrients are required by microorganisms in relatively large amounts. Over 95% of microbial cell dry weight is made up of a few major elements: carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus, potassium, calcium, magnesium, and iron, these are the Macroelements/Macronutrients. Carbon, oxygen, hydrogen, nitrogen, sulfur, phosphorus- C, O, H, N, S, and P- are components of carbohydrates, lipids, proteins, and nucleic acids.

Potassium, calcium, magnesium, and iron exist in the cell as cations and play a variety of roles. Potassium (K⁺) is required for activity by a number of enzymes, including some of those involved in protein synthesis. Calcium (Ca2⁺), contributes to the heat resistance of bacterial endospores among other functions. Magnesium (Mg2⁺) serves as a cofactor for many enzymes, complexes with ATP, and stabilizes ribosomes and cell membranes. Iron (Fe2⁺and Fe3⁺) is a part of cytochromes and a cofactor for enzymes and electron-carrying proteins.

Micronutrients or trace elements : Micronutrients or trace elements are required in small amounts for all microorganisms, in addition to macroelements. These include manganese, zinc, cobalt, molybdenum, nickel, and copper and are needed by most cells. These are required in such small amounts that they are available as contaminants from water, glassware, and regular media components. Often these are adequate for growth.

In nature, micronutrients are ubiquitous and probably do not usually limit growth. 

Micronutrients are normally a part of enzymes and cofactors, and they aid in the catalysis of reactions and maintenance of protein structure. For example, zinc (Zn2⁺) is present at the active site of some enzymes but can also be involved in the association of regulatory and catalytic subunits.  (e.g., E. coli aspartate carbamoyl transferase). Manganese (Mn2⁺) aids many enzymes that catalyze the transfer of phosphate groups. Molybdenum (Mo2⁺) is required for nitrogen fixation, and cobalt (Co2⁺) is a component of vitamin B12.

            Microorganisms may have particular requirements according to the environment or as part of their morphology. For example, bacteria/ archaea growing in saline lakes and oceans require high concentrations of sodium ion (Na⁺). Diatoms need silicic acid (H₄SiO₄) to construct their beautiful cell walls of silica [(SiO₂)n].

In general, microorganisms require a balanced mixture of nutrients. If an essential nutrient is in short supply, microbial growth will be limited regardless of the concentrations of other nutrients.

  

Requirements For Carbon, Hydrogen, Oxygen, And Electrons

All organisms need carbon, hydrogen, oxygen, and a source of electrons. Carbon is needed for the skeletons or backbones of all the organic molecules which make the organisms. Hydrogen and oxygen are also important elements found in organic molecules. Electrons are needed for electron transport chain and for other oxidation-reduction reactions which can provide energy for use in cellular work. Electrons are also needed to reduce molecules during biosynthesis (e.g., the reduction of CO₂ to form organic molecules).

Molecules serving as carbon sources also provide hydrogen and oxygen. Thus, the requirements for carbon, hydrogen, and oxygen are satisfied together. However, one carbon source, carbon dioxide (CO₂), supplies only carbon and oxygen because CO₂ is the most oxidized form of carbon, lacks hydrogen, and is unable to donate electrons during oxidation-reduction reactions. So it cannot be used as a source of hydrogen, electrons, or energy.

Organisms that use CO₂ as their sole or principal source of carbon are called autotrophs. Because CO₂ cannot supply their energy needs, they must obtain energy from other sources, such as light or reduced inorganic molecules.

Heterotrophs are organisms that use reduced, preformed organic molecules as their carbon source. They can also obtain hydrogen, oxygen, and electrons from the same molecules. Thus, organic carbon sources also provide electrons to be used in electron transport as well as in other oxidation-reduction reactions, so heterotrophs use their carbon source as an energy source also.

The more reduced the organic carbon source (i.e., the more electrons it carries), the higher its energy content. Thus, lipids have a higher energy content than carbohydrates.

Heterotrophic microorganisms can use many carbon sources. There is no naturally occurring organic molecule that cannot be used by some microorganism. Actinomycetes, common soil bacteria, will degrade amyl alcohol, paraffin, and even rubber. Some bacteria can use almost anything as a carbon source; for example, Burkholderia cepacia can use over 100 different carbon compounds. Microbes can degrade even relatively indigestible human-made substances such as pesticides. This is usually carried out by complex microbial communities (microbial consortia). These molecules sometimes are degraded in the presence of a growth-promoting nutrient that is metabolized at the same time—a process called cometabolism. Other microorganisms can use the products of this breakdown process as nutrients.

But some microbes are extremely fastidious and catabolize only a few carbon compounds. Cultures of methylotrophic bacteria metabolize methane, methanol, carbon monoxide, formic acid, and related one-carbon molecules. Parasitic members of the genus Leptospira use only long-chain fatty acids as their major source of carbon and energy.

Requirements For Nitrogen, Phosphorus, And Sulfur

Microorganisms require large quantities of nitrogen, phosphorus, and sulfur for growth. These elements may be acquired from the same nutrients/organic sources that supply carbon, or from other inorganic sources.

Nitrogen is needed for the synthesis of amino acids, purines, pyrimidines, some carbohydrates and lipids, enzyme cofactors, and other substances. Many microorganisms can use the nitrogen obtained in amino acids (organic source). Others incorporate ammonia directly through the action of enzymes such as glutamate dehydrogenase or glutamine synthetase and glutamate synthase. Most phototrophs and many chemotrophic microorganisms reduce nitrate to ammonia and incorporate the ammonia in a process known as assimilatory nitrate reduction (inorganic sources) A variety of bacteria (e.g., many cyanobacteria and the symbiotic bacterium Rhizobium) can assimilate atmospheric nitrogen (N₂) by reducing it to ammonium (NH₄). This is called nitrogen fixation.

Phosphorus is present in nucleic acids, phospholipids, nucleotides like ATP, several cofactors, some proteins, and other cell components. Almost all microorganisms use inorganic phosphate as their phosphorus source and incorporate it directly. Low phosphate levels can limit microbial growth in many aquatic environments. Some microbes, such as Escherichia coli, can use both organic and inorganic phosphate. Some organophosphates such as hexose 6-phosphates can be taken up directly by the cell. Other organophosphates are hydrolyzed in the periplasm by the enzyme alkaline phosphatase to produce inorganic phosphate, which then is transported across the plasma membrane.

Sulfur is needed for the synthesis of substances like the amino acids cysteine and methionine, and some carbohydrates, biotin, and thiamine. Most microorganisms use sulfate (inorganic source) as a source of sulfur and reduce it by assimilatory sulfate reduction. A few microorganisms require a reduced form of sulfur such as cysteine (organic source).

Growth Factors

Some microorganisms have the enzymes and biochemical pathways needed to synthesize all cell components using minerals and sources of energy, carbon, nitrogen, phosphorus, and sulfur. Some lack one or more of the enzymes needed to manufacture some indispensable constituents. So, they must obtain these constituents or their precursors from the environment. Organic compounds that are essential cell components or precursors of such components but cannot be synthesized by the organism are called growth factors. There are three major classes of growth factors:

(1) amino acids, (2) purines and pyrimidines, and (3) vitamins.

Amino acids are needed for protein synthesis; purines and pyrimidines for nucleic acid synthesis. Vitamins are small organic molecules that usually make up all or part of enzyme cofactors and are needed in only very small amounts to sustain growth.

 

Functions of Some Common Vitamins in Microorganisms
Vitamin	Functions	Microorganisms Requiring Vitamin
Biotin	Carboxylation (CO2 fixation) One-carbon metabolism	Leuconostoc mesenteroides Saccharomyces cerevisiae
Cyanocobalamin (B12)	Molecular rearrangements	Lactobacillus spp.
Folic acid	One-carbon metabolism	Enterococcus faecalis
Pyridoxine (B6)	Amino acid metabolism (e.g., transamination)	Lactobacillus spp.
Niacin (nicotinic acid)	Precursor of NAD and NADP	Haemophilus influenzae
Riboflavin (B2)	Precursor of FAD and FMN	Dictyostelium spp

 

Some microorganisms require many vitamins; for example, Enterococcus faecalis needs eight different vitamins for growth.

Other growth factors required are; heme (from hemoglobin or cytochromes) is required by Haemophilus influenzae, and some mycoplasmas need cholesterol.

Understanding the growth factor requirements of microbes has significant practical applications. Microbes with known, specific requirements and those that produce large quantities of a substance (e.g., vitamins) are useful.

Microbes with a specific growth factor requirement can be used in bioassays for the factor they need. A typical assay is a growth-response assay, which allows the amount of growth factor in a solution to be determined. The amount of growth in a culture is related to the amount of growth factor present. Ideally, the amount of growth is directly proportional to the amount of growth factor; if the growth factor concentration doubles the amount of microbial growth doubles. 

For example, Lactobacillus and Streptococcus can be used in microbiological assays of most vitamins and amino acids. Microbiological assays are specific, sensitive, and simple. They still are used in the assay of substances like vitamin B₁₂ and biotin, despite advances in chemical assay techniques.

Microorganisms which are able to synthesize large quantities of vitamins can be used to manufacture these compounds for human use. Several water-soluble and fat-soluble vitamins are produced partly or completely using industrial fermentations. Good examples of such vitamins and the microorganisms that synthesize them are

·       riboflavin (Clostridium, Candida, Ashbya, Eremothecium)

·       coenzyme A (Brevibacterium)

·       vitamin B12 (Streptomyces, Propionibacterium, Pseudomonas)

·       vitamin C (Gluconobacter, Erwinia, Corynebacterium)

·       carotene (Dunaliella)

·       vitamin D (Saccharomyces).

Research focuses on improving yields and finding microorganisms that can produce large quantities of other vitamins.

Nutritional Types of Microorganisms

Depending on how the need for carbon, energy, and electrons is fulfilled microorganisms can be classified. 

With respect to their preferred source of carbon, there are heterotrophs or autotrophs. There are only two sources of energy available to organisms: Phototrophs use light as their energy source; chemotrophs obtain energy from the oxidation of chemical compounds (either organic or inorganic). Microorganisms also have only two sources of electrons. There are Lithotrophs (i.e., “rock-eaters”) which use reduced inorganic substances as their electron source, and organotrophs which obtain electrons from reduced organic compounds.

Sources of Carbon, Energy, and Electrons
Carbon Sources
Autotrophs	CO2 sole or principal biosynthetic carbon source
Heterotrophs	Reduced, preformed, organic molecules from other organisms
Energy Sources
Phototrophs	Light
Chemotrophs	Oxidation of organic or inorganic compounds
Electron Sources
Lithotrophs		Reduced inorganic molecules
Organotrophs		Organic molecules

 

In spite of the great metabolic diversity seen in microorganisms, most can be placed in one of five nutritional classes based on their primary sources of carbon, energy, and electrons.

 

Major Nutritional Types of Microorganisms
Nutritional Type	Carbon Source	Energy Source	Electron Source	Representative Microorganisms
Photolithoautotrophy (photolithotrophic autotrophy)	CO2	Light	Inorganic e- donor	Purple and green sulfur bacteria, cyanobacteria
Photoorganoheterotrophy (photoorganotrophic heterotrophy)	Organic carbon but CO2 may also be used	Light	Organic e- donor	Purple nonsulfur bacteria, green nonsulfur bacteria
Chemolithoautotrophy (chemolithotrophic autotrophy)	CO2	Inorganic chemicals	Inorganic e- donor	Sulfur-oxidizing bacteria, hydrogen-oxidizing bacteria, methanogens, nitrifying bacteria, iron-oxidizing bacteria
Chemolithoheterotrophy/ mixotrophy (chemolithotrophic heterotrophy)	Organic carbon, but CO2 also used	Inorganic chemicals	Inorganic e-donor	Some sulfur-oxidizing bacteria (e.g., Beggiatoa)
Chemoorganoheterotrophy (chemoorganotrophic heterotrophy)	Organic carbon	Organic chemicals often same as C source	Organic e-donor often same as C source	Most non photosynthetic microbes, including most pathogens, fungi, many protists, and many archaea

 

The majority of microorganisms are either photolithotrophic autotrophs or chemoorganotrophic heterotrophs.

Photolithotrophic autotrophs (often called photoautotrophs or photolithoautotrophs) use light energy and have CO₂ as their carbon source. Photosynthetic protists and cyanobacteria use water as the electron donor and release oxygen. Other photolithoautotrophs, such as the purple and green sulfur bacteria, cannot oxidize water but get electrons from inorganic donors like hydrogen, hydrogen sulfide, and elemental sulphur.

Chemoorganotrophic heterotrophs (often called heterotrophs or chemoheterotrophs, or chemoorganoheterotrophs) use organic compounds as sources of energy, hydrogen, electrons, and carbon. Usually, the same organic nutrient will satisfy all these requirements. All pathogenic microorganisms are chemoheterotrophs.

The other nutritional classes are very important ecologically though they have only fewer known microorganisms. Some photosynthetic bacteria (purple and green bacteria) use organic matter as their electron donor and carbon source. These photoorganotrophic heterotrophs (photoorganoheterotrophs) are common in polluted lakes and streams. Some of these bacteria also can grow as photoautotrophs with molecular hydrogen as an electron donor.

Chemolithotrophic autotrophs (chemolithoautotrophs), oxidize reduced inorganic compounds such as iron, nitrogen, or sulfur molecules to derive both energy and electrons for biosynthesis. Carbon dioxide is the carbon source.

Chemolithoheterotrophs, also known as mixotrophs, use reduced inorganic molecules as their energy and electron source, but derive their carbon from organic sources. Chemolithotrophs contribute greatly to the chemical transformations of elements (e.g., the conversion of ammonia to nitrate or sulfur to sulfate) that continually occur in ecosystems.

 A particular species usually belongs in only one of the nutritional classes, but some show great metabolic flexibility and alter their metabolic patterns in response to environmental changes.

For example, many purple nonsulfur bacteria act as photoorganotrophic heterotrophs in the absence of oxygen but oxidize organic molecules and function chemoorganotrophically at normal oxygen levels. When oxygen is low, photosynthesis and chemoorganotrophic metabolism may function simultaneously. This sort of flexibility seems complex and confusing, but it gives these microbes an advantage if environmental conditions frequently change.

 Conclusion

     Microorganisms require about 10 elements in large quantities for the synthesis of macromolecules. Several other elements are needed in very small amounts and are parts of enzymes and cofactors.

     All microorganisms can be placed in one of a few nutritional categories on the basis of their requirements for carbon, energy, and electrons.

 

Remote sensing & Geographic information system (RS & GIS)

 Environmental Impact Assessment is the systematic identification and evaluation of the potential impacts (effects) of proposed projects plans, programmes or legislative actions on the total environment. EIA identifies methods to minimize the adverse impacts to improve the project viability. Environmental Impact Assessment (EIA) considers land use, land price, population density, socio-economic level, road accessibility, railway accessibility, air quality, ground water quality, noise level, biological content, historical value, archaeological and visual importance etc.

RS and GIS are ideal tools for environmental monitoring.

Remote Sensing and Geographical Information System (GIS) are the latest technologies or support systems or tools which will produce much more accurate results and perform various geographic analyses even in complex situations.

Remote Sensing and GIS technique is more comfortable, easy and accurate and complete the EIA of any proposed developmental activity in less time. GIS and remote sensing could be used in environmental monitoring for land use analysis, wetland assessment and ground water modelling, habitat mapping, disaster management

Remote sensing is the art and science of making measurements of the earth using sensors on airplanes or satellites.

Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object and thus in contrast to on-site observation.

Remote sensing is used in numerous fields, including geography, land surveying and most Earth Science disciplines (for example, hydrology, ecology, oceanography, glaciology, geology); it also has military, intelligence, commercial, economic, planning, and humanitarian applications.

Remote sensed imagery is integrated within a GIS.

Geographic information system or GIS is a system designed to capture, store, manipulate, analyze, manage, and present spatial or geographic data.

GIS has many applications related to engineering, planning, management, transport/logistics, insurance, telecommunications, and business.

 

Remote Sensing

Science and art of acquiring information (spectral, spatial, and temporal) about material objects, area, or phenomenon, without coming into physical contact with the objects, or area, or phenomenon under investigation. It is important in acquiring data for effective resource management and can be applied to environment monitoring and management. It can be used for acquiring data in more efficient way which is beneficial in quick change detection and effective resource management.

Remote sensing, is  the process of inferring surface parameters from measurements of the electromagnetic radiation (EMR) from the Earth’s surface. This EMR can either be reflected or emitted from the Earth’s surface. In other words, remote sensing is detecting and measuring electromagnetic (EM) energy emanating or reflected from distant objects made of various materials, so that we can identify and categorize these objects.

Remote sensing provides a means of observing large areas and has extensive applications in environmental monitoring, urban planning, civil engineering, disaster management services such as flood and drought warning and monitoring, damage assessment in case of natural calamities, etc.

Principles of Remote Sensing

Different objects reflect or emit different amounts of energy in different bands of the electromagnetic spectrum. The amount of energy reflected or emitted depends on the properties of both the material and the incident energy. Detection and discrimination of objects or surface features is done by studying the reflected or emitted electromagnetic radiation from the object. A “sensor” (e.g., cameras and scanners) mounted on a “platform” (e.g., aircrafts and satellites) detects the reflected or emitted electro-magnetic radiation from an object. Data acquired by RS is interpreted with the help of GIS software‘s.

 Remote sensing technology may be divided into three phases:

•        data collection from a sensor mounted on a platform eg. a satellite;

•        data handling;

•        data interpretation which end up in producing some thematic maps of the investigated surfaces.

Main stages in remote sensing are:

A. Emission of electromagnetic radiation · The Sun or an EMR source located on the platform

B. Transmission of energy from the source to the object · Absorption and scattering of the EMR while transmission

C. Interaction of EMR with the object and subsequent reflection and emission

D. Transmission of energy from the object to the sensor

E. Recording of energy by the sensor · Photographic or non-photographic sensors

F. Transmission of the recorded information to the ground station

G. Processing of the data into digital or hard copy image

H. Analysis of data

 

Passive/ Active Remote Sensing

Depending on the source of electromagnetic energy, remote sensing can be classified as passive or active remote sensing.

 Sun is the naturally available source of energy in passive remote sensing. Most of the remote sensing systems work in passive mode using solar energy as the source of EMR. Solar energy reflected by the targets at specific wavelength bands are recorded using sensors onboard air-borne or space borne platforms.

 In the case of active remote sensing, energy is generated and sent from the remote sensing platform towards the targets. The energy reflected back from the targets are recorded using sensors onboard the remote sensing platform. Most of the microwave remote sensing is done through active remote sensing.

  

Remote sensing platforms

Remote sensing platforms can be placed at different elevations from the Earth’s surface  and are classified accordingly:

· Ground level remote sensing - Ground level remote sensors are very close to the ground. They are used to develop and calibrate sensors for different features on the Earth’s surface.

· Aerial remote sensing

o Low altitude aerial remote sensing

o High altitude aerial remote sensing

· Space borne remote sensing

o Space shuttles

o Polar orbiting satellites

o Geo-stationary satellites

From each of these platforms, remote sensing can be done either in passive or active mode

Advantages of remote sensing are:

a) Provides data of large areas

b) Provides data of very remote and inaccessible regions

c) Can obtain imagery of any area over a continuous period of time through which the any anthropogenic or natural changes in the landscape can be analyzed

d) Relatively inexpensive than employing a team of surveyors

e) Easy and rapid collection of data

f) Rapid production of maps for interpretation

 

Disadvantages of remote sensing are:

a) The interpretation of imagery requires a certain skill level

b) Needs cross verification with ground (field) survey data

c) Data from multiple sources may create confusion

d) Objects can be misclassified or confused

e) Distortions may occur in an image due to the relative motion of sensor and source

 

 Geographical Information System

A geographic information system captures, stores, analyses, manages and presents data, which is linked to locations or having spatial distribution. Functions of GIS include data entry, display, management, information retrieval and analysis. A system of hardware, software and procedures to facilitate the management, manipulation, analysis, modelling, representation, display of geo-reference data to solve complex problems regarding planning and management of resources.

It is a computer-based system that provides four sets of capabilities to handle geo-reference data, such are:

•        data capture: graphic data by digitization or data loaded from existing data files

•        data storage and manipulation: file management and editing

•        data analysis: database query, spatial analysis and modelling

•        data display: maps and reports

GIS is becoming simpler to use and much cheaper to buy that it is hard to imagine a future for environmental monitoring systems without it. GIS is a tool for management, manipulation, analysis, modelling, representation of geographical information recorded with the help of RS.

Data entry, data display, data management, information retrieval, and analysis are the functions of GIS.

Data acquisition is the process of identifying and collecting the data required for the application. After data acquisition, the methods used to convert a dataset into a suitable format for input into the GIS is known as pre-processing. 

Preprocessing is the data format conversion- digitization of maps and printed records and recording this data into a computer database; map projection, data reduction and generalization, error detection, and interpolation. Data sets are manipulated before and after entering into the computer to have a common geometric coordinate, orientation and scale. 

GIS software‘s e.g; ERDAS, ArcView, ArcGIS, SWAT -improves image quality, overlapping etc. The datasets can be manipulated as needed by the analysis.

Many types of analyses are feasible within a GIS; mathematical combinations of layers and complex simulations using the GIS as a database.

•        Final output of GIS is fully classified map or image which is easy to understand.

•       Geographical Information System (GIS), is composition of traditional sciences, contemporary science and technology.

•        A GIS can manage different data types occupying the same geographic space.

•        The major advantage of GIS is that it can read and analyze different layers of information in the form of maps and satellite images easily and allows identifying the spatial relationships.

Advantages of GIS

On the basis of GIS,

•        the digital data base is developed and can be used in future and any related information can be extracted conveniently and efficiently.

•        New information overlaps can be incorporated with newly defined condition.

•        GIS is a powerful tool for handling data collected from a variety of sources at different scales and resolution.

•        Large quantities of data can be stored, maintained and retrieved with a greater speed and low cost.

•        GIS is extremely helpful in planning scenarios, decision models and interactive processes

•        Remotely sensed data used for resource mapping, monitoring and management.

Applications of Remote Sensing & Geographical Information System 

1. GIS is effectively used in the management of spaces for different housing projects. Space management which is a major issue concerning the provision of limited space to meet housing goals, minimize operating costs and promote an effective and productive environment.

2. The suitable site selection is the primary and essential part of eco-city/housing projects planning. GIS can be utilized to visualize whether a particular site meets the predefined criterions or not. GIS techniques help to generate several important functional maps for the master plan such as the location of the waste management sites, green space, parks and open areas etc.

3. Housing and construction industry is one of the major sources for Green House Gas (GHG) emission. GIS technique helps in monitoring GHG emission from the construction activities. The maps generated from several sources could be overlaid to prepare the emission scenario and its impact on settlements.

4. Many applications are enhanced by the use of 3-D spatial information, such as visualization of planning development proposals, flood predictions, tourist visit simulations and the design of transportation networks.

Some GIS software also predicts the future growth with the help of modelling techniques. The applications of remote sensing and GIS in Environmental Impact Assessments are numerous including environmental impact and compliance studies, site investigations and characterizations, emergency planning, monitoring, transportation, telecommunication site, and water and power plant site selection etc.

1. Flooding, environmental degradation and climate studies.

2. Agriculture and Precision Farming.

3. In the Health Sector and Paramedics.

4. In the Mining and Extractive Industry

5. City planning, Transportation, Communication Network designs and in Aviation Industry.

6. Traffic and Accident control and prevention.

7. Planning and Re -Planning program (Slum Re-settlement).

8. Crime Mapping and hot-spots delineations.

9. Land use and Land cover Studies for sustainability.

10. General Developmental control and resource inventory and allocations.

11. Emergency planning and alternative route development.

12. Development of agronomical data and early warning data for food security issues.

13. Deforestation and A forestation studies and preservation of wild life and biodiversity.

14. Engineering mapping

15. Surface water mapping

16. Land use planning and management

17. Environmental impact studies

18. Natural resource mapping

19. coastal zone management

20. In irrigation

21. In air, water, noise, and soil management and planning

22. solid waste disposal etc