eChapters

Abstract

Being an obligate photoautotroph, cyanobacteria must cope with a wide range of fluctuating environmental factors, including high light and ultraviolet radiation (UVR) that may lead to oxidative stress by upsetting the cellular redox status. Photo-induced oxidative stress by means of oxidizing agent such as reactive oxygen species (ROS) may damage several biological processes. In response to several adverse effects of solar UVR, cyanobacteria have developed different strategies such as heat dissipation mechanisms, synthesis of UV- absorbing/screening compounds and antioxidant systems to overcome the detrimental effects of intracellular oxidant molecules. This review deals with UV-induced oxidative stress and their counteracting mechanisms operating in cyanobacteria.

Abstract

A transect was performed along the Chubut River (Patagonia) from the Atlantic towards the Andes measuring major water parameters of this drainage area. Samples were taken at different locations of the Chubut River, and also brooks several Andes lakes in the Chubut and Río Negro Provinces as well as from several Andes rivers and mountain creeks. For comparison, the Laguna Cacique Chiquichano in Trelew (Chubut) was investigated. Several physico-chemical parameters were determined (pH, oxygen, nitrogen compounds, conductivity, redox potential, water hardness and spectral transmission), as well as photosynthesis by means of PAM fluorimetry. Water toxicity was assessed with a bioassay based on toxicity-induced changes of the movement behavior of a flagellate.

Abstract

In order to fill the gap between the protein sequences and their 3D structures available in the public databases, the computational prediction of protein structure has become the need of the hour. Therefore, the present chapter aims to highlight various methods and strategies for computational protein structure prediction by established ab initio, threading and homology modeling methods. Ab initio, threading and homology modeling methods are mainly based on the low sequence similarity, similarity between 25-30% and similarity more than 30% with the template structure respectively. Hybrid methods are preferred which club together a number of features such as structural alignments, solvent accessibility and secondary structure informations.

Abstract

The extensive use of antibiotics has raised serious health concern throughout the world due to development of resistance in microbes towards many classes of antibiotics. The emergence of multidrug resistance (MDR) in microbes and lack of novel classes of antimicrobial agents have raised an immediate need to identify new agents with novel mode of action. In addition to novel agents, inhibitors of efflux pumps are being now viewed as one of the most viable management strategy for treating MDR infections. In this concern, plants have always been a source of inspiration for novel drugs.

Abstract

Cyanobacteria, the Gram-negative photosynthetic prokaryotes are able to produce a wide range of secondary metabolites. Some of these metabolites are of general concern due to their toxicity and known as cyanobacterial toxins. These cyanotoxins are reported widely due to human and animal health hazard. On the basis of their toxicological target, these cyanotoxins can be classified into five different groups: hepatotoxins, neurotoxins, cytotoxins, dermatotoxins and irritant toxins (lipopolysaccharides). Hepatotoxins constitute a family of cyclic peptide variants and are classified as microcystins and nodularins. These hepatotoxic peptides possess a high degree of cellular specificity to the hepatocytes with similar mode of action and act as potent inhibitors of protein phosphatases 1 and 2A (PP1 and PP2A).

Abstract

Synonymous and non-synonymous substitution result in isomerization and deformity in protein structure. Both play more or less important role in evolution. Interestingly, cyanobacterial phycobiliproteins (PBPs) are composed of proteins which are coded by codons by mRNA translation. These proteins are categorized into three groups e.g., C-PC, C-PE and C-APC having a and b subunits. The skeleton and arrangement of amino acids in subunits can provide structural and functional integrity of PBPs as well as GC₃ associated substitution of synonymous and non-synonymous codons.

Abstract

The substantial loss in the shielding ozone layer has resulted in an increase in the solar ultraviolet radiation (UVR) on the Earth’s surface, which is detrimental for all living organisms ranging from prokaryotes to eukaryotes, including humans. This has augmented the scientific concern and interest in searching for the photoprotective compounds from diverse organisms. Cyanobacteria, the primitive O2-evolving photosynthetic prokaryotes are solely dependent upon the solar radiation for their energy requirement and thereby have to always face the UV-B stress. UVR affects cyanobacteria either directly or indirectly by inducing oxidative stress. In response, they have evolved the capacity to synthesize, accumulate and metabolize a variety of UV-absorbing compounds such as, mycosporine-like amino acids (MAAs), scytonemin, carotenoids, biopterin glucoside, as a strategy to reduce the direct and indirect damaging effects of UVR.

Abstract

Present implementation of mass spectrometers has allowed developing new approaches in algal research. Soft ionization techniques like atmospheric pressure chemical ionization (APCI), electrospray ionization (ESI), and matrix assisted laser desorption ionization (MALDI) extend the analytical possibilities of mass spectrometry (MS) beyond classical fatty acid analysis by gas chromatography (GC) with electron impact ionization (EI). New MS-based analytical methods have been developed over the last two decades for algal molecule research including membrane lipids, carotenoids, mycosporine-like amino acids and peptides.
 
MS-based Metabololomics approaches have also been used to gain insights into algal biochemistry and physiology. This review aims at highlighting the achievements in algal research gained by using these recent research tools and their future prospects.

Abstract

Twelve different cyanobacteria strains from different locations in Syria were collected and analyzed. They were identified as strains from Anabaena, Nostoc, Phormidium and Chroococcus. All strains produce mycosporine-like amino acids (MAAs) as UV-screens upon UV-radiation. Composition of the MAAs and amount of UV-induced MAA production differ between the strains. In order to evaluate the long-term stability of completely encapsulated cyanobacteria aliquots were transferred into hermetically closed vessels. The survival was non-invasively determined by means of pulse-amplitude modulated fluorescence and by delayed fluorescence detection. It was found that 4 strains (one Chroococcus, two Anabaena and one Nostoc species) show photosynthetic performance after 4 years of encapsulation. In addition, many cyanobacteria are desiccation tolerant and are able to fix atmospheric nitrogen. They may play an important role in biological life support systems e.g. in space research.

Abstract

Cyanobacteria have gained a lot of attention in recent years because of their novel applications in biotechnology, besides their well recognized role as inoculants for rice crop. They represent favourite model organisms for a deeper understanding of several plant and microbial metabolic processes and efficient systems for the production of recombinant compounds of pharmaceutical and commercial value. They have been identified as a rich source of biologically active compounds with antiviral, antibacterial, antifungal and anticancer activities, which illustrate their potential as biocontrol agents. The genus Anabaena assumes significance not only as a diazotroph, but also as a rich source of pharmacologically active and structurally interesting secondary metabolites with diverse applications in agriculture and industry. The present compilation aims to present an overview of the literature available globally, and studies undertaken in India illustrating the diversity and potential of Anabaena strains, besides their significance in biology and evolution.

In nature, microbes are found as a mixed population. The types that encounter the most favourable environmental and other growth conditions emerge in abundance while others that find the environment less favourable are fewer in number. However, for any kind of study on them or for their use as a pure species, they have to be separated from other species. The nutritional media or culture media are different for different species. As the medium is specific for certain species, it checks or restricts the growth of other microbes for which it may not be suitable. However, some growth of and contamination by unwanted species may occur.

Biofertilizer is still an unclear term. It can be easily found that biofertilizers are identified as plant extract, composted urban wastes, and various microbial mixtures with unidentified constituents, and chemical fertilizer formulations supplemented with organic compounds. Likewise, the scientific literature has a very open interpretation of the term biofertilizer representing everything from manures to plant extracts.  Quality control of biofertilizers involves several major aspects such as isolation and identification of various strains, screening of the pure isolated strains, fermentation and quality control and finished product.

14.1 Introduction

The green revolution brought amazing consequences in food grain production but with insufficient concern for agricultural sustainability. The availability and affordability of fossil fuel based chemical fertilizers at farm level in India have been ensured only through imports and subsidies which are largely dependent on GDP of the country. Dependence on chemicals for future agricultural needs would result in further loss in soil health, possibilities of water contamination and calculated burden on the fiscal system. Indiscriminate synthetic fertilizer usage has polluted the soil, water basins, destroyed micro-organisms and eco-friendly insects, made the crop more susceptible to diseases and depleted soil fertility at the primary levels as of today (Pindi, 2012). India is an agricultural based country.

Earthworms have been on the earth for over 20 million years. In this time they have faithfully done their part to keep the cycle of life continuously moving. Their purpose is simple but very important. They are nature’s way of recycling organic nutrients from dead tissues back to living organisms. Many have recognized the value of these worms. Ancient civilizations, including Greece and Egypt valued the role earthworms played in soil. The Egyptian Pharaoh, Cleopatra said, “Earthworms are sacred.”

Most trees legumes thrive in tropical regions but N2 fixing non leguminous trees are prevalent in temperature conditions. Callatiam and coworkers from U.K. cultivated Frankia for the first time in 1978 in pure culture. A number of non-leguminous shrubs and trees as Alnus, Myrics, Hippophae, Casuarina and Elaeagnus are nodulated by N₂ fixing Actinomycetes, Frankia with Frankiaceae (Actinomycetes), the only acyinomycete reported to fix nitrogen to date. The so called actinorhizal plants include 7 orders, 8 families, 17 genera and 173 species of dicotyledons plants reported by Gaur, (2010), whereas 200 plants and 23 genera were reported by Diagne et al. (2013). Some of the important non-leguminous families and genera are given in Table 12.1.

11.1 Introduction

Our Country is a fast developing nation for the overall development and has proved that the country which was known for a begging bowl for food grains has turned up towards self-sufficiency and also has excess production to feed the present level of population. From about 50 MT of food grain production in 1950-51, harvest in 2010-11 reached over 241 MT, highest ever along with high production of fruits, vegetables, milk, egg and fish. This increased food production in the country has mainly been achieved through productivity gains, as the net sown area has remained static for the last four decades.

Phosphorus is the second important key element after nitrogen as a mineral nutrient in terms of quantitative plant requirement (Donahue et al., 1990), which is required in optimum amount for proper growth of plants and soil micro-organisms. Being a constituent of ATP, it is involved in various processes such as cell division, energy transduction through photosynthesis and biological oxidations and uptakeof nutrients. The average soil contains 0.05% phosphorus, but only one tenth (1/10) of this is available to plants due to its poor solubility and chemical fixation in soil (Barber, 1984). About 98% of Indian soils have inadequate supply of available phosphorus (Ghosh and Hassan, 1979). A survey of Indian soils showed that out of 363 districts, only 2.2% were high, 51.5% medium and 46.3% were low in phosphorus content (Ghosh, 1982).

BGA belong to a class of prokaryotic photosynthetic microorganisms also known, as cyanobacteria are capable of fixing atmospheric nitrogen aerobically. Most abundantly found in tropical zone, never form fibrous growth and are enveloped by a sheath. The trophic independence of algae for C and N makes them responsible for a natural fertility buildup of rice field soils. The nitrogen fixing ability of BGA was first recognized by Frank and Prantil in 1889. The occurrence of the BGA in the rice field was reported by FE Fritsch in 1907.

Azospirillum is a spiral-shaped nitrogen fixing bacterium. It also produces hormones and vitamins. Important species are Azospirillum brasilense and Azospirillum lipoferum. It is widely distributed in soils and grass roots.The genus Azospirillum belongs to family Spirillaceae with four commonly available species viz. A. brasilence, A. lipoferum, A. amazonense and A. halopraeferens or A. seropedicae (Fig. 8.1).

The first species of the genus Azotobacter, named Azotobacter chroococcum family Azotobacteriaceae, was isolated from the soil in Holland in 1901. Azotobacter represents the main group of heterotrophic free living nitrogen-fixing bacteria principally inhabiting neutral or alkaline soils. Azotobacter chroococcum and Azotobacter agilis were studied by Beijerinck (1901). In subsequent years several other types of Azotobacter group have been found in the soil and rhizosphere such as Azotobacter vinelandii, Lipman (1903); Azotobacter beijernckii, Lipman (1904); Azotobacter paspali, Döbereiner (1966), Azotobacter nigricans, Krasil’nikov (1949); Azotobacter armenicus, Thompson and Skerman (1981); Azotobacter salinestris, Page and Shivprasad (1991). A. paspali while A. agilis was categorized  under the genus Azomonas (Table 7.1).