Marine Microbiology

Bioactive Compounds and Biotechnological Applications

Se-Kwon Kim

• Publisher: Wiley-VCH
• Year: 2013
• Print ISBN: 9783527333271
• eBook ISBN: 9783527665273
• Edition: 1
• Topic: Sciences biologiques
• Subtopic: Biologie marine

Deliberately breaking with the classical biology-centered description of marine organisms and their products, this reference emphasizes microbial technology over basic biology, setting it apart from its predecessors. As such, it systematically covers the technology behind high-value compounds for use as pharmaceuticals, nutraceuticals or cosmetics, from prospecting to production issues.

Following a definition of the field, the book goes on to address all industrially important aspects of marine microbial biotechnology. The first main part contains a description of the major production organisms, from archaebacteria to cyanobacteria to algae and symbionts, including their genetic engineering. The remaining four parts look at commercially important compounds produced by these microorganisms together with their applications. Throughout, the emphasis is on technological considerations, and the future potential of these organisms or compound classes is discussed. A valuable and forward-looking resource for innovative biotechnologists in industry as well as in academia.

1

Introduction to Marine Actinobacteria

Panchanathan Manivasagan, Jayachandran Venkatesan, and Se-Kwon Kim

1.1 Introduction

Marine microbiology is developing strongly in several countries with a distinct focus on bioactive compounds. Analysis of the geographical origins of compounds, extracts, bioactivities, and Actinobacteria up to 2003 indicates that 67% of marine natural products were sourced from Australia, the Caribbean, the Indian Ocean, Japan, the Mediterranean, and the Western Pacific Ocean sites [1].

Marine Actinobacteria have been looked upon as potential sources of bioactive compounds, and the work done earlier has shown that these microbes are the richest sources of secondary metabolites. They hold a prominent position as targets in screening programs due to their diversity and their proven ability to produce novel metabolites and other molecules of pharmaceutical importance [2]. Since the discovery of actinomycin [3], Actinobacteria have been found to produce many commercially bioactive compounds and antitumor agents in addition to enzymes of industrial interest [4]. Approximately, two-third of the thousands of naturally occurring antibiotics have been isolated from these organisms [5]. Of them, many have been obtained from Streptomyces [6] and these natural products have been an extraordinary source for lead structures in the development of new drugs [7].

Although the diversity of life in the terrestrial environment is extraordinary, the greatest biodiversity is in the oceans [8]. More than 70% of our planet's surface is covered by oceans and life on Earth originated from the sea. In some marine ecosystems, such as the deep sea floor and coral reefs, experts estimate that the biological diversity is higher than that in the tropical rainforests [9]. As marine environmental conditions are extremely different from the terrestrial ones, it is surmised that marine Actinobacteria have characteristics different from those of terrestrial counterparts and, therefore, might produce different types of bioactive compounds. The living conditions to which marine Actinobacteria had to adapt during evolution range from extremely high pressures (with a maximum of 1100 atmospheres) and anaerobic conditions at temperatures just below 0 °C on the deep sea floor to high acidic conditions (pH as low as 2.8) at temperatures of over 100 °C near hydrothermal vents at the mid-ocean ridges. It is likely that this is reflected in the genetic and metabolic diversity of marine actinomycetes, which remain largely unknown. Indeed, the marine environment is virtually an untapped source of novel Actinobacteria diversity [10, 11] and, therefore, of new metabolites [12–14].

However, the distribution of Actinobacteria in the sea is largely unexplored and the presence of indigenous marine Actinobacteria in the oceans remains elusive. This is partly caused by the insufficient effort put into exploring marine Actinobacteria, whereas terrestrial Actinobacteria have been, until recently, a successful source of novel bioactive metabolites. Furthermore, skepticism regarding the existence of indigenous populations of marine Actinobacteria arises from the fact that the terrestrial bacteria produce resistant spores that are known to be transported from land into sea, where they can remain available but dormant for many years [15–17]. In this chapter, we evaluate the current state of research on the biology and biotechnology of marine Actinobacteria. The topics covered include the abundance, diversity, novelty and biogeographic distribution of marine Actinobacteria, ecosystem function, bioprospecting, and a new approach to the exploration of actinobacterial taxonomic space.

1.2 Actinobacteria

Actinobacteria are aerobic, nonmotile, and Gram-positive bacteria with high guanosine–cytosine (GC) content in their DNA (70–80%) and are phylogenetically related to the bacteria based on the evidence of 16S ribosomal RNA cataloging studies [18]. Although originally considered an intermediate group between bacteria and fungi, they are now recognized as prokaryotic organisms. Actinomycetales is an order of Actinobacteria, which have substrate hyphae and form aerial mycelia and spores. Aerial hyphae of Actinobacteria give rise to sporophores that differ greatly in structure. The spore-bearing hyphae of the aerial mycelium have somewhat greater diameter than the substrate mycelium. The spores are resistant to desiccation and can survive in soil in a viable state for long periods. This stage of the life cycle imparts resistance to adverse environmental conditions in the soil such as low nutrients and water availability. These microorganisms are phenotypically highly diverse and found in most natural environments [18].

1.3 Origin and Distribution of Marine Actinobacteria

Actinobacteria are mostly considered as terrigenous bacteria because of their wide occurrence and abundance in soil. Their distribution in the aquatic environment remained largely undescribed for many years. Most of the workers questioned the indigenous nature of aquatic Actinobacteria because these produce resistant spores that are known to be transported from land into sea and other aquatic bodies where they can remain dormant for many years. In fact, they were considered to originate from dormant spores that were washed from land [18].

It is now clear that specific populations of marine-adapted Actinobacteria not only exist in the marine environment but also significantly add to diversity within a broad range of Actinomycetes taxa [19, 20]. Recent studies have also shown that Actinobacteria can be isolated from mangrove swamps, other coastal environments, and even deep ocean sediments [21, 22].

Despite the fact that the selective methods used to culture Actinobacteria targeted only the mycelium-producing strains, thereby omitting the important marine groups such as the mycolate Actinobacteria [23], it can be seen that marine Actinobacteria include new phenotypes that have clearly diverged from those known to occur on land.

Although the ecological roles of marine Actinobacteria remain undefined, it is possible that like their terrestrial counterparts, they are involved in the decomposition of recalcitrant organic materials such as chitin, a biopolymer that is particularly abundant in the sea [21]. Given that Actinobacteria living in the ocean experience a dramatically different set of environmental conditions compared to their terrestrial relatives, it is not surprising that speciation has occurred and unique marine taxa are now being recognized. Not only the extent of marine actinobacterial diversity is yet to be determined, but also the adaptations of these microbes in the sea resulting in the production of secondary metabolites are to be studied.

1.4 Isolation and Identification of Marine Actinobacteria

Actinobacteria are ubiquitous in marine environment and there are several techniques for their isolation. In the conventional isolation techniques, several factors must be considered, namely, choice of screening source, selective medium, culture conditions, and recognition of candidate colonies in the primary isolation. Some of the researchers employ pretreatments of sediments by drying and heating to stimulate the isolation of rare Actinobacteria [24]. An alternative approach would be to make the isolation procedure more selective by adding chemicals such as phenol to the sediment suspension. Many media have been recommended for isolation of Actinobacteria from marine samples. Specialized growth media have been developed to isolate specific actinomycete genera with macromolecules such as casein, chitin, hair hydrolysate, and humic acid that are carbon and nitrogen sources for obtaining rare Actinobacteria. Several antibiotic molecules are also used in selective media to inhibit unwanted microbes, including fast-growing bacteria and fungi.

Strains are preliminarily indentified according to their morphological criteria, including characteristics of colonies on the plate, morphology of substrate mycelium and aerial hyphae, morphology of spores, pigments produced, cell wall chemo type, whole-cell sugar pattern, and so on, and their identification is confirmed by 16s rDNA analysis [25–32].

1.5 Indigenous Marine Actinobacteria

The indigenous deep sea Actinobacteria warrant some specific consideration because if we can define some or all of the features of the deep sea Actinobacterial physiology, this should lead to greater efficacy of isolation. Although an obligate requirement for Na+ and the obligate requirements or tolerance of oligotrophic substrate concentrations, low temperatures, and elevated pressures for growth would provide prima facie evidence of indigenicity, to our knowledge no systematic testing of this hypothesis with respect to deep sea Actinobacteria has been made. In addition, demonstration of growth or metabolic activity in situ should be made. We believe that physiological understanding of this type could enable more precise ...

Table of contents

• Cover
• Related Titles
• Title Page
• Copyright
• Preface
• Biography
• List of Contributors
• Chapter 1: Introduction to Marine Actinobacteria
• Chapter 2: Treasure Hunting for Useful Microorganisms in the Marine Environment
• Chapter 3: Strategy of Marine Viruses in Global Ecosystem
• Chapter 4: Taxonomic Study of Antibiotic-Producing Marine Actinobacteria
• Chapter 5: Marine Cyanobacteria: A Prolific Source of Bioactive Natural Products as Drug Leads
• Chapter 6: Marine Bacteria Are an Attractive Source to Overcome the Problems of Antibiotic-Resistant Staphylococcus aureus∗
• Chapter 7: Marine Bacteria as Probiotics and Their Applications in Aquaculture
• Chapter 8: Small-Molecule Antibiotics from Marine Bacteria and Strategies to Prevent Rediscovery of Known Compounds
• Chapter 9: Marine Bacteriophages for the Biocontrol of Fish and Shellfish Diseases
• Chapter 10: Marine Actinomycetes as Source of Pharmaceutically Important Compounds
• Chapter 11: Antimicrobial Agents from Marine Cyanobacteria and Actinomycetes
• Chapter 12: Bioactive Compounds from Marine Actinomycetes
• Chapter 13: Fungal Bioactive Gene Clusters: A Molecular Insight
• Chapter 14: Anticancer Potentials of Marine-Derived Fungal Metabolites
• Chapter 15: Antifungal and Antimycotoxin Activities of Marine Actinomycetes and Their Compounds
• Chapter 16: Antituberculosis Materials from Marine Microbes
• Chapter 17: Harnessing the Chemical and Genetic Diversities of Marine Microorganisms for Medical Applications
• Chapter 18: Marine Symbiotic Microorganisms: A New Dimension in Natural Product Research
• Chapter 19: Application of Probiotics from Marine Microbes for Sustainable Marine Aquaculture Development
• Chapter 20: Antimicrobial Properties of Eicosapentaenoic Acid (C20 : 5n−3)
• Chapter 21: Bioprospecting of Marine Microbial Symbionts: Exploitation of Underexplored Marine Microorganisms
• Chapter 22: Marine Microorganisms and Their Versatile Applications in Bioactive Compounds
• Chapter 23: Metabolites of Marine Microorganisms and Their Pharmacological Activities
• Chapter 24: Sponges: A Reservoir for Microorganism-Derived Bioactive Metabolites
• Chapter 25: Bioactive Marine Microorganisms for Biocatalytic Reactions in Organic Compounds
• Chapter 26: Marine Microbial Enzymes: Biotechnological and Biomedical Aspects
• Chapter 27: Biomedical Applications of Mycosporine-Like Amino Acids
• Index