The role of micro-organisms

If we collected all the living material on Earth and weighed it, half of the accumulated biomass would be microorganisms.  That’s a lot of cells: about 5x10^30 of them. Microbes live everywhere, deep in the world’s oceans and crust to glaciers perched on mountain peaks. They are found in every conceivable habitat, from the soil that we use to grow our food to our digestive systems that we use to digest our food.

Microbes are the oldest group of organisms on the Earth.Microbes were the first living organisms on Earth; they have been around for at least 3.8 billion years – 80% of the Earth’s 4.6 billion year history. Compare that to the dinosaurs, which lived on earth for only 165 million years, or 3.5% of the Earth’s history!

Oxygen was absent from the Earth’s early atmosphere, so the first bacteria were anaerobic.

These early Earthlings were probably similar to purple and green bacteria that persist today.

Photosynthetic microbes, those that could use the energy from the sun to synthesize biological molecules, probably arose about a billion years later.

These were similar to today’s purple photosynthetic bacteria.

These groups, however, did not produce oxygen during photosynthesis.

a billion years later Oxygenic phototrophs ancient cyanobacteria first appeared.

These microorganisms oxygenated the Earth’s atmosphere, paving the way for the evolution of multi-cellular life.

MAJOR MICROBIAL GROUPS The world of microorganisms is made of bacteria, fungi,

algae, protozoa, and viruses.

They are group together only because of their small size, and not by their function. If, for example, the same taxonomical rules were applied to larger animals, some fish, shrimp, green plants, birds and mammals would be grouped together.

Some microorganisms such as viruses, bacteria, and protozoa are notoriously small, under one mm. Others, like algae and fungi, have large size relatives (such as the brown algae that is among the largest living organisms).

Unlike larger organisms, the morphology of microorganisms is relatively poor and is confined to few shapes and colours. However, their poor morphology is compensated by great physiological versatility.

VIRUSES

They cannot live independently, and only multiply inside the cells of other organisms. However, their demand for a host is fairly specific. For example, it is unlikely that a crustacean virus will attack humans or fish. Viruses are also the simplest of all organisms and are made of nucleic acid (either DNA or RNA), frequently coated with a protein layer.

Clever Pinterest Virus

Viruses are very small, ranging between 0.01 and 0.03 microns, and only visible by using an electron microscope.

ALGAE Algae are photosynthetic

organisms (contain chlorophyll) and obtain their energy from the sun and their carbon from carbon dioxide.

Their size ranges from one micron to many meters.

All organisms that use carbon dioxide for their carbon requirement are called autotrophs.

Algae are generally beneficial in aquaculture by supplying oxygen and a natural food base for the cultured animals.

FUNGIFungi are similar to algae, but they do not contain chlorophyll and require pre-formed organic matter as energy and carbon sources (e.g., sugars, fat, protein, and other carbohydrates). Such organisms are called heterotrophs. Fungi, ranging in size from a few microns to several centimetres, grow either independently by feeding on decaying matter, or in association with plants and animals.

Orange Peel Fungus Laetiporus gilbertsonii Clavarioid fungi spikey-fungi

PROTOZOAProtozoa are heterotrophs, mostly free-living, feeding mainly by devouring smaller microorganisms. Their size ranges between two and 200 micron meters. A large group of protozoa, the Sporozoa, are parasites. Small numbers of protozoa contain chlorophyll and can switch between autotrophic and heterotrophic modes of feeding, based on light conditions.

BACTERIA Bacteria range in size from 0.1 to 15 micron, with some " giants "that may reach half a millimeter. They make up the most metabolically diverse group of living organisms. Although some are parasitic to animals and plants, the majority of bacteria are free-living, having either a neutral or beneficial relationship with humans and other animals and plants. Their metabolic versatility is incredible: while most are heterotrophs, using either light or chemical energy. One of their most remarkable characteristics is their ability to multiply rapidly, with generation times usually ranging between minutes to hours.

Cellular structure

Micro-organisms are always present in the environment and given the right conditions of food availability, temperature and other environmental factors, they grow and multiply.

generalised pattern of growth of micro-organisms

They form what is termed a 'food chain'. For example inorganic and organic substances in wastes are consumed by bacteria, fungi and algae. These are in turn consumed by protozoa and nematodes (some fungi however trap nematodes) and the latter by rotifers.

Microbes form the backbone of every ecological system by controlling global biogeochemical cycling of elements essential for life.

micro-organisms, such as bacteria, play an important role in the natural cycling of materials and particularly in the decomposition of organic wastes.

What is waste for humans and higher vertebrates becomes a useful food substrate for the micro-organisms

To survive and reproduce in any habitat, microbes must be able to obtain energy, deal with toxins, and handle competitors and predators. These physiological and ecological activities are reflected in the organism’s metabolism. Organisms surviving and reproducing in different habitats are going to face different environmental conditions and so will evolve a wide diversity of metabolisms. Because microbes are found in so many different environments, they represent, collectively, an incredible diversity of metabolisms. Metabolism is a product of the organism’s genes, thus microbes also possess remarkable genetic diversity.Microorganisms contain incredible metabolic and genetic diversity.

MICROBIAL PROCESS

Bacteria and other microorganisms, most notably fungi, are able to metabolize and transform numerous organic and inorganic compounds. Therefore, man has used them for thousands of years for making yogurt, pickles, bread, cheese, wine, and more recently for waste purification and wastewater purification.

The starting materials and the end products of such processes vary based on the microorganisms' capabilities (as reflected in their genetic makeup), and the environment in which these processes occur (e.g., availability of oxygen, temperature, salinity, pH, etc.

Process controlled by microorganisms can occur aerobically (in the presence of oxygen) or anaerobically (with no oxygen present).

Microorganisms are of major important in industrial wastewater treatment, agricultural and aquaculture.

Microorganisms may have positive or negative effects on the outcome of aquaculture operations. Positive microbial activities include elimination of toxic materials such as ammonia, nitrite, and hydrogen sulfide, degradation of uneaten feed, and nutrition of aquatic animals such as shrimp, fish; production of aqua-farmer.

AEROBIC MICROBIAL PROCESS IN AQUACULTUTRE Generally, aerobic microbial processes yield compounds

which can be beneficial, and are either not toxic or have lox toxicity levels in aquaculture ponds or tanks.

Oxidation of organic matter to carbon dioxide, a process which is the main consumer of oxygen in aquaculture ponds or tanks.

Oxidation of ammonia to nitrate via nitrite, which also consumes large quantity of oxygen. oxidation of reduced sulfur compounds (such as hydrogen sulfide and elemental sulfur) to sulfate, a process that generally has low oxygen demand in aquaculture.

Conversion of carbon dioxide to biomass by autotrophic bacteria (such as the nitrifying bacteria) with a relatively small amount of biomass produced in aquaculture facilities, when compared to the conversion of carbon dioxide to biomass by algae.

Conversion of carbon dioxide to biomass by algae depending on the availability of light. Excluding feeding, the photosynthetic process in aquaculture is the main input of carbon source and natural food for aquatic animals. 

AEROBIC MICROBIAL PROCESS IN AQUACULTUTRE

ANAEROBIC MICROBIAL PROCESSES IN AQUACULTUREMicrobial anaerobic processes, if not controlled, can produce compounds that are highly toxic to cultured animals.These processes include: Consumption of organic matter, without the utilization of free

oxygen, resulting in products which are usually not fully oxidized (such as alcohols, organic acids).

Reduction of nitrate and nitrite, which can yield either nitrogen gas or ammonia. In aquaculture, due to the toxicity of ammonia and nitrite, ammonia production is not welcomed, while nitrogen gas production is beneficial.

However, in agriculture, the opposite is true - the conversion of nitrate and nitrite to nitrogen gas result in a loss of fertilizers.

Reduction of sulfur compounds to hydrogen sulfide as a final product, a compound, which is toxic to most animals at even very low concentrations.

Humans fear microbes when they should celebrate them.Most microbes are harmless to humans and some are immensely beneficial. For example, without bacteria, food production as we know it could not exist. Because of microorganisms’ role in nutrient cycling, agricultural production would grind to a halt without microbes. No bacteria? No cheeseburgers! Bacteria are used in food production to make cheese, yogurt, sauerkraut, and pickles. Ruminant animals, including cows, sheep, and goats, are dependent on gut bacteria to digest their diet of plants. Yeast, a eukaryotic microbe, makes our bread, beer, and wine possible.

In the general media, microorganisms have a bad reputation. Some deserve it: microbes are responsible for a number of human diseases, including tuberculosis, malaria, cholera, AIDS, and measles. But harmful microbes, while important, are only a tiny percentage of total microbial diversity.

In a natural water body, e.g. river or lake, the number and type of micro-organisms depends on the degree of pollution. The general effect of pollution appears to be a reduction in species numbers. For example in a badly polluted lake, there are fewer species but in larger numbers, while in a healthy lake there can be many species present but in lower numbers.

No ecological process occurs without the direct or indirect action of microorganisms.

Given the ancient history of microbes, their global distribution, and their metabolic and genetic diversity, it is not surprising that they are involved in all ecological processes on Earth. The types of ecological activities depend on the species composition, population sizes, and physiological states of microbial communities.Microbes play a key role in nutrient cycling in particular. The three main nutrients that all living organisms require are nitrogen, phosphorus, and carbon. Microbiologists estimate that microbes are the largest reservoir of nitrogen and phosphorus stocks on the planet and that they are tied with plants as a carbon reservoir. In addition, microbes are important in the cycling of other nutrients, like sulfur and iron.It is obvious, then, that understanding how microbes function in ecosystems is necessary to have a comprehensive view of how the biological world works. The diversity of microbes, however, is the downfall of efforts to study microbial ecology. Very complex systems, like those in soil, are so diverse that teasing apart relationships between community members is nearly impossible. Less diverse ecosystems, like those in hypersaline environments, provide a simpler place to start understanding microbial communities.

Economic uses and benefits of microorganisms

Microorganisms have been used as tools for the production of products for millennia. Even in ancient times, the ability to produce vinegar by allowing water to percolate through wood shavings was known and widely practiced. Likewise, the transformation of a yeast suspension into beer or a suspension of crushed grapes into wine was common knowledge. The basis of these events may not have been known, but that did not impede the sale or trade of such products.These economic uses of microorganisms are the earliest examples of biotechnology ..

use of the bacterium Lactobacillus acidophilusto produce yogurt,

fermentation of cabbage to produce sauerkraut. to produce a variety of cheeses, and In the agricultural sector, the discovery of the ability

of Rhizobium to convert elemental nitrogen to a form that was useable by a growing plant, led to the use of the microorganism as a living fertilizer that grew in association with the plant species.

sauerkraut yogurt

Economic uses and benefits of microorganisms

manufacture of protein from the nucleic acid templates occurs was pivotal in advancing the use of microorganisms as factories. gene splicing technologies (to remove DNA from one region of the genome and move the DNA in a controlled way to another region of the same DNA, or DNA in a completely different organism (prokaryotic or eukaryotic). ), which can be accomplished by various splicing and reannealing enzymes , or by the use of viruses or mobile regions of viral DNA (such as transposons ) as vectors have allowed biotechnologists to create what are termed "designer genes," which are designed for a specific purpose.

Economic uses and benefits of microorganisms

The gene for the production of human insulin has been transferred into the genome of the common intestinal tract bacterium Escherichia coli .

The example of insulin reflects both the health benefit of the use of microbes and the economic benefit to be realized, since the mass production of insulin that is possible using bacteria lowers the cost of the product.

Economic uses and benefits of microorganisms

A process known as DNA fingerprinting, which relies upon enzymes that are produced and operate in bacteria, has enabled the tracing of the fate of genes in plant and animal populations, and enhanced gathering of evidence at crime scenes.

Economic uses and benefits of microorganisms

Other medical uses of microorganisms, particularly in the production of antibiotics , have been the greatest boon to humans and other animals. The list of maladies that can now be treated using microbiologically derived compounds is lengthy, and includes cystic fibrosis, hemophilia,hepatitis B, Karposi's sarcoma, rejection of transplanted organs, growth hormone deficiency, and cancer. The worldwide sales of medical and pharmaceutical drugs of microbial origin now exceeds U.S. $13 billion annually.Microorganisms have also been harnessed as factories to produce compounds that are used in areas as divers as textile manufacture, agriculture, and nutrition. Enzymes discovered in bacteria that can exist at very elevated temperatures (thermophilic, or "heat loving" bacteria) cab be used to age denim to produce a "pre-washed" look. Similar enzymes are being exploited in laundry detergent that operates in hot water. Microorganisms are used to enhance the nutritional content of plants and other food sources. The growing nutraceutical sector relies in part on the nutritional enhancements afforded by microbes. Bacteria are also useful in providing a degree of resistance to plants. An example is the use of Bacillus thuringensis to supply a protein that is lethal to insect when they consume it. The use of bacterial insecticides has reduced the use of chemical insecticides, which is both a cost savings to the producer and less stressful on the environment. Other bacterial enzymes and constituents of the organisms are utilized to produce materials such as plastic.

Economic uses and benefits of microorganisms

The mode of growth of bacterial populations has also proved to be exploitable as a production tool. A prime example is the surface-adherent mode of bacterial growth that is termed abiofilm . Although not known at the time, the production of vinegar hundreds of years ago was, as now, based on the percolation of water through biofilms growing on wood shavings. Immobilized bacteria can produce all manner of compounds. As well, the cells can provide a physical barrier to the flow of fluid. This dynamic aspect has been utilized in a so far small-scale way to increase the production of oil from fields oil thought to be depleted. Bacteria can plug up the zones were water and oil flows most easily. Subsequent pumping of water through the field forces the oil still resident in lower permeability areas to the surface.With the passing of time, the realized and potential benefits of microorganisms and the implementation of strict standards of microbe use, is lessening the concern over the use of engineered microorganisms for economic and social benefit. The use of microorganisms can only increase.

Micro-organisms require cellular building blocks, such as (carbon) C, (hydrogen) H, (oxygen) O, (nitrogen) N, (phosphorus) P, and minerals for growth. These can be obtained through consuming organic substances containing these elements, or from inorganic materials, such as carbon dioxide, water, nitrate and phosphate. Micro-organisms also require energy. They obtain this through respiration. In this process organic carbon is oxidised to release its energy. Oxygen or other hydrogen acceptors is needed for the respiration process. Algae and photosynthetic bacteria can also utilise energy from sunlight, while certain types of bacteria can utilise energy from chemical reactions not involving respiration. The building blocks and energy are used to synthesise more cells for growth and also for reproduction.

In the treatment of wastewater three types of overall processes are distinguished to represent the conversion of organic wastes by micro-organisms. The classification is based on whether the environment where the process takes place is aerobic, anaerobic or photosynthetic. Under aerobic conditions (in the presence of oxygen), micro-organisms utilise oxygen to oxidise organic substances to obtain energy for maintenance, mobility and the synthesis of cellular material. Under anaerobic conditions (in the absence of oxygen) the micro-organisms utilise nitrates, sulphates and other hydrogen acceptors to obtain energy for the synthesis of cellular material from organic substances. Photosynthetic organisms use carbon dioxide as a carbon source, inorganic nutrients as sources of phosphate and nitrogen and utilise light energy to drive the conversion process.

Micro-organisms also produce waste products, some of which are desirable and some undesirable. Gases such as carbon dioxide and nitrogen are desirable, since they can be easily separated and do not produce pollution. Gases such as hydrogen sulphide and mercaptans, although easily separated require treatment for odour. Micro-organisms' cellular materials are organic in nature and can also cause pollution. It would be desirable if the cellular materials have undergone self oxidation (endogeneous respiration utilising own body cells) to produce non-biodegradable materials that are relatively stable. Self-oxidation is achieved when there is no substrate/food available.

The microbiological conversion reactions of organic waste into cellular material can be empirically represented as shown below.(i) Conversion under aerobic conditions (see diagram below):Under aerobic conditions ammonia is further oxidised to nitrate. Phosphorus and sulphur contained in the organic substances are oxidised to phosphate and sulphate. These can be further utilised by the micro-organisms for synthesis.(ii) Conversion under anaerobic conditions (see diagram below):Methane (CH4) is a useful gaseous by-product of anaerobic conversion, because it can be combusted to produce heat/energy. On the other hand if it is released to the atmosphere without being combusted, it contributes to the greenhouse gas effect.

Conversion under photosynthetic conditions

As shown by the conversion reactions (the utilisation of organic wastes for food by micro-organisms) the product is mainly the cellular material of the micro-organisms i.e. more organisms are produced. The growth yield is the weight of micro-organisms produced per unit weight of organic substances consumed by the micro-organisms. The growth yield depends on the type of substrate and environmental conditions. The smaller the value of the growth yield the better it is for waste treatment, because less sludge is produced which requires disposal. Its value is usually between 0.2 and 0.5 for aerobic conversion, while the corresponding value for anaerobic conversion is smaller.

Source: Boundless. “Role of Microbes in Biogeochemical Cycling.” Boundless Microbiology. Boundless, 12 Aug. 2015. Retrieved 21 Sep. 2015 from https://www.boundless.com/microbiology/textbooks/boundless-microbiology-textbook/microbial-ecology-16/microbial-ecology-192/role-of-microbes-in-biogeochemical-cycling-961-10506/