but has not been possible yet. Here, we describe the coral core microbiome and demonstrate clear phylogenetic and functional divisions between the micro-scale, niche habitats within the coral host. In doing so, we discover seven distinct bacterial phylotypes that are universal to the core microbiome of coral species, separated by thousands of kilometers of oceans. The two most abundant phylotypes are co-localized specifically with the corals’ endosymbiotic algae and symbiontcontaining host cells. These bacterial symbioses likely facilitate the success of the dinoflagellate endosymbiosis with corals in diverse environmental regimes. This book primarily focuses on selecting positive and effective interactive core microbiome that are both phenotypically and genotypically very adaptive and sustainable, which further improve crop quality and productivity vis-à-vis sustainable agriculture. The bioengineering concept for rhizosphere improvement has also been discussed in one of the chapters. The book also highlights the structure, characterization, and biotechnological application of aquatic core microbiomes.
Javid A. Parray
PhD, PDF
1 A Review of Endophytic Microbiota of Medicinal Plants and Their Antimicrobial Properties
Robeena Sarah, Nida Idrees, and Baby Tabassum
Toxicology Laboratory, Department of Zoology, Govt. Raza P.G. College, Rampur 244901, India
1.1 Introduction
Medicinal plants have been used in many parts of the world for thousands of years in traditional treatments for numerous diseases. In rural areas of developing countries, they are still used as a primary source of drugs [1]. About 80% of developing countries use conventional medicines for general health care [2]. Natural products can be obtained from medicinal plants that have proven to be a rich source of biologically active compounds; many of them are used to develop novel chemicals for the pharmaceutical industry. With regard to disease-causing microorganisms, the increasing resistance to therapeutic agents currently in use, such as antibiotics and antiviral agents, has led to renewed interest in exploring novel anti-infective compounds. As approximately 450,000 plant species are available worldwide, of which only one per cent has been phytochemically analyzed, the prospects of locating new bioactive compounds are tremendously positive.
Medicinal plants are essentially considered complex and dynamic when used in systems for remedial therapy. Hence, their chemical composition depends upon several factors, such as botanical species, genetically determined chemotypes, anatomically a part of the plant (e.g., seed, flower, root, and leaf), storage, sun exposure, humidity, kind of ground, time of harvesting, and ecological area. Moreover, biogenic factors, such as the fungal and bacterial endophytes related to diverse parts of the plant, can influence their chemical composition. In recent years, the research and study of the multiple interactions occurring between endophytes and medicinal plants have modernized our knowledge of plant biology, with entirely unexpected and remarkable application perspectives: the probability of modulating, amplifying, or interfering within the biosynthesis of phytoconstituents (e.g., terpenes, polyphenols, and alkamides), but also to engineer the synthesis of latest molecules directly, for instance with antibiotic activity.
1.2 Antimicrobial Properties of Medicinal Plants with Particular Reference to Neem (Azadirachtaindica)
There are many reports on conventional medicinal plants and natural products to treat several diseases. Many plant-based medicines utilized in traditional therapeutic systems as agents in the treatment of infectious diseases are recorded in pharmacopoeia, a variety of which have been investigated recently for their efficiency against disease-causing microorganisms. The general antimicrobial activities of medicinal plants and their products, such as essential oils, were analyzed earlier [3,4].
Moreover, medicinal plants also can play an elementary function against rising antibiotic resistance both directly for their antimicrobial activities (e.g., antibacterial, antiviral, antifungal, and antiparasitic ones) and indirectly by reducing resistance against antibiotics.
There are numerous medicinal plants with well-known antimicrobial activity, including traditional Chinese or Ayurvedic medicine. Among medicinal plants adopted in experimental studies, a classic example is the Azadirachta indica (Figure 1.1) commonly known as neem, an evergreen tree of the sub-tropics and tropics, indigenous to the Indian subcontinent, with a recognized ethnomedicinal value and significance in agriculture and also in the pharmaceutical industry [5]. Every part of the neem plant, such as leaves, fruits, seeds, bark, and roots, contains compounds with proven antioxidant, anti-inflammatory [6], antidiabetic, antibacterial, antigingivitic, antifungal, anticancer, antiviral, antiulcer, neuroprotective, antipyretic, hepatoprotective, nephroprotective, and wound-healing properties. It possesses incredible potential within the field of medicine, pest management, and environmental protection. Neem may be a natural source of eco-friendly herbal pesticides, insecticides, and agro-based chemicals [7]. The impact of mouthwash containing neem on plaque and gingivitis was analyzed in a clinical study, indicating that it may help maintain mouth hygiene and suggest an enhanced effect on preventing oral diseases since it is both cost-effective and easily accessible [8]. Approximately 400 compounds are isolated from various parts of neem until now, and significant bioactive secondary metabolites and relatively 30 compounds are isolated from endophytes of neem [5]. Endophytic fungi of neem produce a wide range of secondary bioactive metabolites with potential compounds, namely, melanin, antimicrobial, antioxidant, anti-inflammatory, insecticides, nematicides, etc. [5].
Figure 1.1 Medicinally important parts of the Azadirachta indica (neem) tree showing flowers; fruits; twigs; bark and leaves.
Neem imposes a check on microbial growth and, in the breakdown of cell membrane capability, exhibits antimicrobial properties [9]. Neem nanoemulsion displayed antibacterial activity by disturbing the integrity of the bacterial cell membrane against strains of a bacterial pathogen. Different parts of the plant reveal antimicrobial properties against a wide range of pathogenic microbes [10]. Neem extract has shown antimicrobial effects against Streptococcus mutans and S. faecalis [11]. A new vaginal contraceptive, NIM-76, obtained from neem oil, has shown an inhibitory effect on the growth of various pathogenic microorganisms, including fungi, bacteria, and viruses [12]. The antibacterial property of neem seed oil in vitro against 14 strains of pathogenic bacteria has been recently assessed [13].
1.3 Current Trends on Bioactive Metabolites from Endophytic Microbiota of Medicinal Plants
A significant development in the understanding of plant-associated microbiota has been prompted by massive DNA sequencing technology in the past decade. Such close connection of microorganisms with plants has a broad contribution to plant nutrient absorption, growth, stress tolerance, and health status, and secondary metabolite production [14]. Metal hyper-accumulating plants are known to shelter a co-evolved microbiota [15,16], and an essential role has been recognized in microbial-assisted phytoremediation [17]. Medicinal plants are well-known to shelter endophytes that are potentially concerned with the biosynthesis of phytoconstituents and can synthesize bioactive compounds.
The composition of biologically active components of medicinal plants differs broadly depending on their soil type, plant species, and their association with microorganisms [18,19]. These plant-linked microbial communities and their physiological functions are also strongly influenced by bioactive secondary metabolites synthesized by medicinal plants [20–22]. Moreover, for specific character and activities, including growth, nutrient acquirement, induced systemic resistance, and tolerance to abiotic stress factors, plants depend on their microbiome
