Sponge associated Microbes & its Biotechnological potential - A way to sustainable development

Balaram Mohapatra, Environmental Microbiology Lab
Department of Biotechnology, Indian Institute of Technology (IIT), Kharagpur, 721302

Microorganism shapes the biosphere by their unique geochemical activity and diversity. They make possible the cycles of carbon, nitrogen, oxygen and sulfur that take place in terrestrial and aquatic systems. They are also a source of nutrient at the base of all ecological food chains. The terrestrial as well as marine ecosystem harbors a great microbial biodiversity. More than 70% of our planet is covered with ocean and life also originated from it. Experts estimated that biological diversity in ocean and sea floor is higher than tropical rainforests, so ocean forms an environment with greatest biodiversity. It is known that only 0.1-1% of the microbial diversity and their potential has been explored so it is important to take insight into marine microbial community for its potential use in environmental sustainability.

As the ocean called "Mother of origin", investigations onto the deep sea environment have demonstrated the presence of a significant microbial community buried deep within sediments and plays major role in global cycling of elements and contains a large reservoir of organic carbon. Paradoxically, the oceans represent the earth's last environment to be explored for its microbiology. Recent studies on deep sub-seafloor biosphere have shown that the living condition to which marine microbes had to adopt range from extreme high pressure (1100 atm), anaerobic condition at temperature below 00 C on deep sea floor, to high acidic condition (pH - 2 to 3), and temperature above 1000 C at hydrothermal vents. So it is likely that marine ecosystem represents a great diversity of microorganism. Due to presence of good bicarbonate buffering system, differential flux rate of light, inorganic salts, organic carbon sources, other elements in trace and vast array of associative higher organisms, the fertility is high in marine ecosystem.

Marine microbiology encompasses the study of microbes that live in not only the superficial marine waters but also the abyssal depth from the coastal to the offshore regions, from the general oceans to the specialized niches like the blue waters of the tropical coral reefs ecosystems to the black smokers of hot thermal vents. Marine microorganisms have developed unique metabolic and physiological capabilities that not only ensure survival in extreme environments but also offer potential for production of metabolites not seen in terrestrial microorganisms. They have proven to produce a variety of chemically interesting and biologically significant secondary metabolites and some of them are expected to serve as lead compounds for drug development or pharmacological tools for basic studies of life sciences. Studies have also suggested that some bioactive compounds isolated from marine invertebrates such as sponges, coelenterates, mollusks or proto-chordates are truly originating from symbiotic microorganisms (example bacteria, fungi, blue-green algae, and dino flagellates).

MARINE SPONGES: Perfect partner for symbiosis
Sponges belong to Phylum Porifera, of kingdom Animalia. Sponge bodies are diverse in form, ranging from encrusting sheets, to volcano-shaped mounds, to tubes as small as one millimeter or as large as one meter. In all cases, sponges have a canal system, through which they pump water. Water enters through pores called ostia, flows through canals to a spacious chamber called a spongocoel, and finally exits through large openings called oscula. Sponges filter food particles out of the water flowing through them. Particles larger than 50 micrometres cannot enter the ostia and pinacocytes consume them by phagocytosis (engulfing and internal digestion). Particles from 0.5 to 50 micrometres are trapped in the ostia, which taper from the outer to inner ends. These particles are consumed by pinacocytes or by archaeocytes which partially extrude themselves through the walls of the ostia. Bacteria-sized particles, below 0.5 micrometres, pass through the ostia and are caught and consumed by choanocytes. Since the smallest particles are by far the most common, choanocytes typically capture 80% of a sponge's food supply.

Sponges and symbiotic Microbes
The major beneficial roles of symbiont in sponges are:
• Phototrophic symbionts play a major role in providing total energy requirement for the sponge
• Other than nutrition phototrophic symbiont also provide light shielding effect to sponge
• Sponge symbionts may affect the nitrogen metabolism of their hosts
• Another role of symbionts (both autotrophic & heterotrophic) is the production of potentially active useful chemical compounds such as antibiotic, anti-fungal compounds & compound that prevent predation or fouling.

A wide variety of secondary metabolites were isolated from sponges and these have been associated with antibacterial, antimicrobial, antiviral, antifouling, HIV-protease inhibitor, HIV reverse transcriptase inhibitor, immunosuppressant and cytotoxic activities. In addition to potential anticancer applications, the MNPs of sponges have a myriad of activities ranging from antibiotic activity including anticoagulant, antithrombin, anti-inflammatory, as well as immunomodulatory activities.

Marine organisms comprise approximately half of the total biodiversity on the Earth and the marine ecosystem is the greatest source to discover useful therapeutics. In recent years, a significant number of novel metabolites with potent pharmacological properties have been discovered from marine organisms.

Antibiotics: Chemotherapeutic agents usually obtained from living organisms and refers to metabolic product of one microorganism, which is bactericidal or bacteriostatic to another. The major points of attack of antibiotics on micro- organisms include;
• Inhibition of cell wall synthesis.
• Damage to the cytoplasmic membrane.
• Inhibition of nucleic acid and protein synthesis.
• Inhibition of specific enzyme systems.

Sponge produces a wide variety of antibacterial substances due to microbes associated with it.

Probiotics: It is defined as live microbial feed supplements that improve health of man and terrestrial / aquatic livestock with biocontrol of pathogens. Antagonism as a matter of fact seems to be common among marine bacteria. An antonym of antibiotics, probiotics involves multiplying few good/ useful microbes to compete with harmful ones, thus suppressing their growth. These include certain bacteria and yeasts that promote life which have been in continuous since a long time. Probiotics are living microorganisms supplemented in food or feed which render beneficial effects on the intestinal microbial balance. Sometimes they are also referred to as biotherapeutic agents because of their antibiotic nature. Probiotic bacteria have been the focus of much scientific and commercial interest due to the range of possible health effects as listed below:

• Increased nutritional value (better digestibility, increased absorption of minerals and vitamins)
• Promotion of intestinal lactose digestion.
• Positive influence on intestinal flora.
• Prevention of intestinal tract infections (bacteria or viruses induced enteritis, Helicobacter pylori ulcers/ neoplasis)
• Regulation of intestinal motility (prevents constipation irritable bowel syndrome)
• Improvement of immune system.
• Prevention of certain types of cancer recurrence.
• Reduction of harmful products eliminated by kidney and liver.
• Prevention of artherosclerosis by decreasing harmful blood cholesterol.
• Prevention of Osteoporosis.
• Improves mineral absorption.

Vitamins and PUFAs: Most vitamins and related biofactors are at present or mainly produced by organic chemical synthesis e.g. Vitamin A, cholecalciferol (D3), tochopherol (E), Menaquinone (K2), thiamin (B1), niacin (PP or B3), pantothenic acid (B5), pyridoxine (B6), biotin (H or B8), folic acid (B9) or by extraction processes e.g. β- carotene, vitamin E, polyunsaturated fatty acids and vitamin F group. However for several of these compounds (β -carotene, vitamin E, vitamin F group), micro algal culture procedures and microbiological processes (for vitamin K2, B1, PP, B5, B6, B8) rapidly emerged and some are already competing with existing chemical processes, especially the micro algal derived fat soluble vitamins like provitamin A, vitamin E and the PUFAs.

Antifouling Agents: Microorganism secretes chemicals that prevent larvae of other marine organisms from settling and growing on them. New molecular tools provide the opportunity to improve our fundamental understanding of the interaction between fouling organisms and biofilms formation, which in turn will lead to novel strategies to control biofouling.

Biopolymers and Biosurfactant: These substances have tremendous application value in food and petroleum industries. The microbial colonization of the surface appears to depend on the ability of the microbe to adhere to the surfaces. A marine isolate of Acinetobacter was found to produce a surfactant "EMULSAN" which was later commercialized. The product was successfully marketed as a chelating agent for oil tankers and oil storage tanks. This compound has also the ability to complex with uranium, which may find application in recovery of uranium from waste material. These polymers are also useful in Enhanced Oil Recovery (EOR).

Biomoniters: Marine organisms can provide the basis for development of biosensors, bio-indicators, and diagnostic devices for medicine, aquaculture, and environmental monitoring. Bacterium Salmonella is employed for detection of fecal pollution in potable water. Bacterial bioluminescence is a recent technique used for measurement of gaseous pollutants and other compounds such as CO2, C2H5OH and ethyl acetate. Biomonitor that holds great promise is the gene probe, which can be used to identify organisms that pose health hazards or may be useful in research. Specific gene probes can be employed, for example, to detect human pathogens in seafood.

Biopigments: Increased interest to switch to biopigments in food, beverage, cosmetics, pharmaceuticals and fine chemical sectors than their synthetic chemical counter parts has been a great attempt. Microbes and algae are used for biopigment production. Carotenoids and xanthophylls like beta- carotenes and lycopene, leutin, zeaxanthin, canthoxanthin, rhodoxanthin and asthaxanthin attract full attention of industrial microbiologist.

Bioremediation: Microorganisms used to remove the environmental pollutants i.e. the toxic wastes found in soil, water, air etc. Marine microbes play a key role in removing alkyl suphides, nitrate, nitrite in the wood-pulping industry, degradation of soil fumigants, such as methyl bromide and 1,2 dichloropropane. Several strains of purple- non-sulphur marine bacteria are responsible for mineralization of chlorinated aromatic compound e.g. 2- chlorobenzoic acid, 2-chlorophenol or phenol.

Single Cell Oil: These are derived lipids mostly of tri glycerol types which accumulate in the biological membranes as well as some macro storage molecules in the cytoplasm of certain microorganisms. SCO are now produced by various microorganisms as commercial sources of Arachidonic acid (ARA) and Ducosahexanoic acid (DHA).These oils are now extensively used as dietary supplements in infant formulas. An understanding of the underlying biochemistry and genetics of oil accumulation in such microorganisms is therefore essential if lipid yields are to be improved.

Enzymes: Produced by marine bacteria are important in biotechnology due to their range of unusual properties. Some are salt resistant, a characteristic that is often advantageous in industrial processes (detergents and industrial cleaning application. Several fungi isolated from the coastal area of India have been reported to produce lactase and other lignocellulolytic modifying enzymes. These enzymes are useful in the industries like dairy industry, detergents, oleochemical, synthesis of triglycerides, surfactants, pharmaceuticals, agrochemicals and polymer synthesis.

Marine enzymes are used to study the ion channels, biosensors for detecting environmental pollution, pathogen detection and disease diagnostic in aquaculture. Marine enzymes have also been applied in preparation of organic fertilizer, pollution control like waste water treatment, degradation of plastic, degradation of toxic pollutants e.g. phenol and its methylated derivatives aromatic hydrocarbon and alkanes and bioremediation of fossil fuels.

Concluding Thoughts: One of the major researches are going on the aspects of proteases, lipases and other industrially important enzymes which can act in extreme conditions of pH, temperature for their higher selectivity and specificity. By combined use of Metabolic and genetic engineering of these enzymes can be a better and more reliable way for sustainable development.

About Author / Additional Info:
The author is working as PhD scholar in the department of biotechnology, IIT-Kharagpur, W.B., India-721302. His broad area of research is study of Microbial metabolism of indigenous microbes involved in Arsenic contamination in ground water.