Scope for cognitive research in the study of rhizobacteria and photobacteria
Bacteria & their abilities: Bacteria are prokaryotic, unicellular, microscopic organisms. For us they are invisible mindless, speechless, brainless creatures or lacking many prominent characteristic features such as complex internal structures and abilities of other living things like plants, animals including humans. Despite the absence of such megacellular functions, they have been identified and proved to be functionally very versatile living things. This functional versatility is attributed to their ability to thrive in different environmental conditions employing unlimited adaptive mechanisms and their rapid rate of reproduction/ growth rate. Their ubiquity is another reason for that they are found everywhere on the planet earth. They also inhabit human body, animals and plants. They are found in deserts, oceans, soils of different types, deep thermal vents of high pressure, even the coldest regions of Alaska, in boiling sulfur streams or in extremely polluted environment. Some of them can live without oxygen or can thrive in highly acidic conditions. In addition to this, they carry out all major biochemical functions similar to eukaryotes such as respiration, photosynthesis, reproduction, anabolism and catabolism. They also exhibit unique cellular responses as quorum sensing, signalling, chemotaxis and colony formation. They even synthesize important chemical compounds as growth hormones, enzymes and biomolecules.
What is cognitive research?
The term 'Cognition' is related to various 'mental' processes governed by central nervous system (CNS). Some of the prominent processes include linguistic ability, computing, thinking, and decision making abilities supported by philosophy-psychological concepts. In fact, bacteria do not possess CNS and hence the described related processes. But it would be wise to declare that bacteria do possess cognitive abilities different from eukaryotes instead of labeling them as organisms with noncognitive functions. Research study can be initiated by the recognition of 'microbe specific' cognition mechanisms in photosynthetic and rhizobacterial species. It would also be possible to compare and relate cognition of autotrophic and heterotrophic nutritional groups of bacteria. In this study species of photosynthetic and rhizobacteria would be representative of autotrophic and heterotrophic groups respectively. Signalling studies at inter/ intra species level under different environmental conditions like nutrient stress, physico-chemical constrains or in presence of recalcitrant compounds like petroleum fuels and pesticides would be very informative. Such study will provide great deal of information regarding expression of different phenotypes and genotypes which can be later studied at molecular level using different molecular and psychological diagnostic tools in the laboratory.
Cognitive research in rhizobacteria: Beneficial functions of bacteria are incomparable to any living thing. Without them the functioning of all biological cycles would have been impossible. Bacteria are integral components of carbon, nitrogen, sulfur, oxygen, phosphorus and other geochemical cycles. Bacteria living in vicinity of the plant roots or rhizosphere are called as rhizobacteria. They possess many beneficial traits and interact with plant host. Various plant growth promoting properties of rhizobacteria are biological nitrogen fixation, solubilization of insoluble phosphate compounds, mineralization of organic phosphates, enhanced nutrient uptake and hence plant nutrition, Sequestering and provision of micronutrients like iron, calcium, zinc, copper and manganese in utilizable form, denitrification to reduce excess nitrate load in the soil, exopolysaccharide production to bind soil particle and to retain water potential and aeration, secretion of various plant growth regulating metabolites like auxins, cytokinins, gibberellins, abscisic acid, and ethylene. The increases in germination, seedling emergence, vigor, height, root system development and increased yield are some of the criteria that are the effects of rhizobacteria. Rhizobacteria also maintain plant health of and offers protection from pathogens by biocontrol activities like production of toxic compounds, antibiotics, cyanides to suppress pathogen attack and prevent crop damage caused by phytopathogens. They also interact competitively with other soil micro fauna for nutrients and niche by production of secondary metabolites like antibiotics, chelators like siderophores, bacteriocins and eradicate them to establish and colonize in the plant rhizosphere. Many rhizobacteria represents special traits to live under stress conditions exerted by nutrient limitation, drought, salinity, cold temperature or heavy metal pollution. Such rhizobacteria find immense environmental applications such as rhizoremediation. The important potential rhizobacterial genera include species of Rhizobium, Bradyrhizobium, Acetobacter, Enterobacter, Azotobacter, Azospirillium, Bacillus, Proteus, Burkholderia, Serratia and Pseudomonas. These rhizobacteria have also been essential components of biofertilizers. Another type of rhizobacteria is deleterious bacteria like Agrobacterium sp. and Pseudomonas syringae which do not promote plant growth but they are opportunistic plant parasites. They compete for nutrients present in the rhizosphere, reduce root growth, nutrient uptake and inhibit seed germination. Despite their harmful properties, they have been exploited for integrated pest management and weed control measures.
Cognitive research for photobacteria: Photosynthetic bacteria (photobacteria) like Purple sulfur bacteria (Chromatium sp.), Purple non-sulfur bacteria (Rhodospirillum rubrum) and Green bacteria (Chlorobium sp.) resemble prokaryotic blue green algae/cyanobacteria, plants and higher algae regarding requirement for large amount of energy in the form of ATP (Adenosine Tri-phosphate). But they are different with respect to the form of chemical reductants and resultant end products of photosynthesis. Bacterial photosynthesis is anoxygenic means oxygen is not end product like that in plants, algae and cyanobacteria. Phototrophic bacteria utilize light energy in nutrition and inorganic compounds such as H2 or H2S and organic compounds lactate, succinate or malate are reductants of bacterial photosynthesis. Photobacteria could have multiple biotechnological applications such as production of enzymes and pharmaceuticals for the one simplest reason that no carbon source needs to be added in their growth medium. Photosynthetic bacteria find potential application in bioremediation of polluted aquatic environments since they can grow and utilize toxic substances like H2S or H2S2O3.
It can be concluded from above descriptions that bacteria exhibit basic biological functions as well as interactive abilities such that competition, mutualism, symbiosis, commensalism, parasitism or antagonism. It indicates that they are sensitive, adaptive, communicative and even decisive. The present description of these 2 types of bacteria suggests that bacteria possess the most basic cognition mechanism and that is cooperation. A bacterial colony which contains millions of bacterial cell actually represents a neatly coordinated network of signals which are translated to perform intended function. Thus plant growth promotion is not a function of single bacterium but actually a cascade of well coordinated interactions among bacterial species, different genera and the surrounding environment. Theories of cognitive science like parallel subsystems, logical operations, auto-amplification and cross talk which have been illustrated for human neural network could actually be demonstrated in bacteria. Thus size of bacteria is not the matter but all basic cognitive functions seem to be configurated in these small living creatures and hence represent an ideal, easy to handle and replicable model system to estimate the cognition basics in the laboratory. The scientific study and information regarding cognitive science of bacteria and other microbes is very scanty and therefore, it certainly demands in detail research investigations.
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