Classification of Living Organisms
Actinobacteria are a group of gram positive bacteria having high G+C content in their DNA. It is one of dominant phyla. Many bacteria in this phylum are pleomorphic in their morphology. Several pathogenic genera are found in actinobacteria, such as Mycobacterium species causing tuberculosis and leprosy. It includes some of most common soil life fresh water life and marine life playing an important in decomposition of organic molecules playing vital role in organic matter turn over and carbon cycle. Some members are known for peculiar odor from soil after rain called as petichor found mainly in warm environment. They have high pharmological and commercial value because of their secondary metabolite nature. The genera Streptomyces, Frankia, Actinomyces and Nocardia are often called Actinomycetes ,because they have a radiate star like ,form of growth by reason of their often branching filaments. Their morphology superficially resembles with fungi. This morphology improves its ability to absorb nutrients in highly competitive soil environment. Mostly they are aerobic , few are anaerobic.
They have richest morphological differentiation which is based on filamentous degree of organization . These characters are basis of phylogenetic systematics. It has various culture characteristics ,controlled by relevant genes.
Substrate mycelium grows on medium or its surface. Its main function is absorption of nutrients for growth of actinobacteria. Microscopically seen they are slender, transparent and branched. These are of different colors likewise orange , blue, red,green,black,white and yellow etc. these colors are helpful in identification of new species.
It is that substrate mycelium that develops to certain stage and grows in air. Aerial hyphae have fibrous sheath except the genera Pseudonocardia and Amylocota.
The substrate mycelium grows to aerial hyphae then develops into spore bearing mycelium which is reproductive hyphae. It can be monosporous,oligospourous and polysporous. Its chain length ,colors and position helps in classification. For example Nocardia brevicatene forms short chains of 2-7 spores. Genus Streptomyces is polysporous.
Division Of hyphae and production of spore starts with cross wall formation process. Firstly hyphae fragments. Spores are formed by septation and disarticulation of pre existing hyphal elements within a hyphal sheath e.g Genus Streptomyces.
Spores 1-2?m thick, ,rod shaped, coliform, globose,allantois and reniform motile spores have flagella. For example Kinecoceus radio tolerance is monotrichous and Catemulioplanes japonicas is peritrichous.
Sporangium is a sac like structure in which spores are developed and held until they release leaving empty envelope.
Stability of morphological characters
Morphological characters due to gene regulation are generally quite stable and it is important basis of classification.
Phylogenetic framework and molecular signature for main clades of phylum actinobacteria
Analysis of glutamine synthetase sequence has been suggested for phylogenetic analysis of actinobacteria .Actinobacteria have many important human pathogens and also give rich sources of natural product including many antibiotics and other component of scientist interest .Thus a reliable phylogeny of large phylum and means to identify its groups are valuable. Detailed phylogenetic and comparative analyses of more than 150 actinobacterial genomes are reported. In phylogenetic trees, basis of 35 conserved proteins, resolved main groups of actinobacteria.
Habitat, diversity, functional roles and environmental adaptations
Habitat have been isolated from diverse ecosystems ,including alkaline saline soil ,marine sponge and deep sea subunits ,hot springs ,fresh water and medicinal plants .Due to their diverse ecological functions they have broad applications potential in agriculture and environmental protection apart from antibiotics. During last few decades actinobacterial resource research has focused on special habitats and external environment. Under harsh conditions they not only shows extensive taxonomic diversity but high genetic diversity of biosynthetic pathways for synthesis of new biological compounds .They are found in volcano ,deserts and cold springs .Their biogeographically isolation and biogeochemical factors are mainly influencing its distribution .It is found in inner tissue of marine coralsa ,a special habitat of actinobacteria. They are important with respect to antibiotics and buffering of soil.
Genomics of actinobacteria
They are pathogens, soil inhabitants, plant commensals and GIT commensals .It is impossible to identify most bacterial groups of actinobacteria due to their diversity. Genome sequence analysis helped in study of genes, physiology and evolutionary aspects of actinobacteria .some of streptomyces was mistaken as fungi but genomics showed that they were bacteria not fungi. The class actinobacteria is deadly pathogenic and at the same time most important in antibiotic production .Mycobacterium tuberculosis ,second leading cause of death while streptomyces are source of bioactive metabolites source .Genus Corneybacterium is pleomorphic .The production of secondary metabolites help them to survive in harsh environment .Genes make up genome and genome make biosynthetic gene clusters. The whole genome of six genera is compared.
They are non endospore forming rods and aerobic .Myco means fungus because of their filamentous growth they show acid fast staining ,pathogenecity and drug resistance .They have mycolic acid in their cell wall giving resistance against water, and because of waxy layer nutrients entry is made slow and it shows slow growth. It includes, Mycobacterium tuberculosis which causes tuberculosis and mycobacterium leprae causing leprosy .A number of other species are present in a soil and water and are occasional pathogens.
Corneybacterium (club shaped) tends to be pleomorphic. They show changing morphology often with age .The best example is Corneybacterium diptheriae, causative agent of diphtheria.
It is named because it produces propionic acid. Some of its species are important in swiss cheese formation .Propionibacterium acne cause acne.
It shows high pleomorphic morphology and gram variability that’s why difficult to assign a taxonomic position. Gardnrella vaginalis cause one of most important form of vaginalis.
The genus frankia cause nitrogen fixing nodules to form in alder tree roots much as rhizobia cause nodules in roots of legumes.
It is best known genus of actinomycetes and it is isolated from soil. They are strict aerobes .The reproductive asexual spores are formed at ends of aerial filaments .This characteristically produces geosmin . They are valuable because they produce commercial antibiotic .This has led to intensive study of genus there are 500 described species.
It consists of facultative anaerobes that are found in mouth and throat of humans and animals. They form filaments that can fragment for example Actinomyces israelii cause actinomycosis, a tissue destroying disease4 affecting head, neck or lungs.
It resembles actinomyces morphologically, however they are aerobic .Their structure resembles with cell wall of mycobacterium they are often acid fast .They are commonly found in soil . Nocardia asteroides cause chronic pulmonary infection ,also cause mycetoma ,a localized destructive infection of feet and hands.
It is common, indent progressively invasive caused by organisms belonging to Phylum Actinobacteria in order actinomycetales.
It is sub acute to chronic bacterial disease characterized by slowly inflammation development of draining sinus tracts may discharge sulphur granules .It involves cervicofacial area ,thorax or abdomen including pelvis but rarely CNS ,skin or bone. It has worldwide distribution and it is more commonly in males.
It is complex in two respects.
1. Principle agent does not belong to single species
2. Action lesion contains 1-10 bacterial specie.
Its risk factors are poor oral hygiene .It cause dental decay ,orofacial trauma ,periodontal abscesses slowly enlarged masses.Risk factors are as follows
* Mandible (53%)
* Cheek (16.4%)
* Upper jaw (5.7%)
* Mandibular jaw (0.3%)
There can be thoracic actinomycosis that affects abdomen ,GIT ,CNS ,bone and skin.
* Locked jaw
* Weigh loss
* Lumps on neck and face
* Draining sores on skin
* High sinus drainage
* Chest pain
Actinomyces israelii ,actinomyces naeslundi ,actinomyces viscous and actinomyces odontolyticus causes actinomycosis.
* Damaged immune response
* Neglects dental care after dental surgery
* Trauma to mouth or jaw
* Women who have used IUT (Intra uterine device) for birth control are at higher risk
It is diagnose from fluid, tissue sample or sample from affected area .Diagnosis shows yellowish granules.
Primary treatment is by antibiotics. More often penicillin is given but if one is allergic to it its alternatives like tetracycline ,clindamycin ,erythromycin. If it prolongs then surgery is done.
* Good oral hygiene
*Regular visits to dentists
Nocardia disorder infect lungs ,brain and skin. It occurs mainly in persons with weakened immune system.
It is caused by aerobic actinomyces specie Nocardia asteroids and Nocardia brasiliensis (Pyhlum Actinobacteria).
* Weigh loss
* Night sweats
* Chest pain
* Lung infection
* Headache, weakness ,confusion and seizures
* Skin ulcers
* Lymph nodes
Exams and tests
The health care provider examines the sample tissue. Brain biopsy , bronchoscopy and skin biopsy is done.
* Diabetic patients
* Bone marrow or strong organ transplant
* High level of corticosteroids
* Antibiotics-6 months to year
* Surgery to drain pus in skin or tissue
* High dose of sulfonamides if resistant alternatives like ampicilin ,erythromycin and minocyclin is given.
Microbial Anatomy and physiology
* At the amino acid level, cmr gene is responsible for resistance in actinomycetes
* Actinobacteria are chemoorganotrophic and play a vital role in the biodegradation and recycling of organic matter.
* Actinobacteria are mainly aerobes with an oxidative metabolism, but several species are facultative anaerobes or even strict anaerobes.
* Actinobacteria are widespread in soil but they are also present in marine and freshwater sediments, mangrove ecosystems and inside plant tissues.
* Most actinobacteria are free?living microorganisms, but several species are important plant and animal pathogens.
* Actinobacteria are unrivaled in their aptitude to produce many useful compounds with application in medicine, agriculture and industry.
* Genomic sequence data has revealed that actinobacteria have the potential to produce far more secondary metabolites than up to that time thought.
It is normal flora of humans and cattle mouth if leads to other areas become pathogenic
* The family Streptomyces is a remarkable source of antibiotics
* The nitrogen fixing bacteria – Frankia
* It has decomposing ability – actinomyces
* Streptomycin is the first antibiotic to cure tuberculosis.
* Streptomyces is two by third of clinically useful antibiotics
* Actinomycetales are useful in breakdown of cellulose and lignin found in exoskeleton of insects. Breakdown of these materials make it reliable to plants.
Geosmin ,a characteristic smell is produced by actinomycetes.
* https www.boundless.com/microbilogy/text books/boundless
* eor.org/page /7861/overview
* study.com/academylessonactinobacteria – definition .characters.html
* ellitottikim.pbworks.com/w/age/18794172/harmful properties
* Microbiology and molecular biology reviews
* Microbiology an introduction by Tortora Funke and Case