Bacterial Diversity of Selected Genuses E-Book

Ankita Kheradia Patadia

• Herausgeber: BookRix
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Veröffentlichungsjahr: 2020

Beschreibung

Microbiology is a diverse discipline.e novice. The traditional books
seem to be too long and detailed to be read by the undergraduatel student who is trying to keep up with several classes simultaneously of other subjects. This book contains all of the information that is useful undergraduate Microbiology studying students who are studying microbiology keeping in mind their examination. 
It cover many aspects of bactrial diversity in depth. The book is divided into eight chapters. The chapters are comprehensive yet free of unnecessary detail and provide the reader with a framework for understanding.
I shall be thankful for any comment or suggestions from students, teachers and all the readers of the book for further improvements. 

Leseprobe

Ankita Kheradia Patadia

Bacterial Diversity of Selected Genuses

Class notes

Words are common, yet incomplete means of acknowledging a person’s gratefulness, to people who had helped us. But still better ways are yet to be invented for expressing our sincere appreciation of the same. Our special vote of thanks to our colleagues. It gives us immense pleasure to recall the timely help, encouragement and discussion extended by them. We would like to say thanks to our friends for their advice and readiness to share their knowledge.This account would be incomplete without the mentioning of our family members, who have supported us during tough period of our lives. They have provided moral support and encouragement whenever we needed. The successful completion of this work involves help from many people directly or indirectly. We thank them all. Last, but definitely not the least, we express our reverence to almighty for giving us the strength, confidence and moral boost for successful completion of this book. ANKITA KHERADIA PATADIABookRix GmbH & Co. KG81371 Munich

Chapter 1 Introduction

The kingdom Monera is also called the kingdom Prokaryotae. It consists of all prokaryotic organisms, including the eubacteria (“true bacteria”), the cyanobacteria, and the archaea.

All monerans are unicellular; they lack true nuclei and generally lack membrane-enclosed organelles. Their DNA has little or no protein associated with it.

Reproduction in the kingdom Monera occurs mainly by binary fission. Of all monerans, the eubacteria are of greatest concern in the health sciences.

Criteria for classifying and studying bacteria

Criteria

Description

Uses

Habitat

Places at its present

Know basic requirement

Morphology

Size and shape of cells; arrangements in pairs, clusters, or

Filaments; presence of flagella, pili, endospores, capsules

Primary distinction of genera

And sometimes species

Staining

Gram-positive, Gram-negative, acid-fast

Separates eubacteria into

Divisions

Growth

Characteristics in liquid and solid cultures, colony morphology,

Development of pigment

Distinguish species and genera

Nutrition

Autotrophic, heterotrophic, fermentative with different

Products; energy sources, carbon sources, nitrogen sources,

Needs for special nutrients

Distinguish species, genera, and

Higher groups

Physiology

Temperature (optimum and range); pH (optimum and range),

Oxygen requirements, salt requirements, osmotic tolerance,

Antibiotic sensitivities and resistances

Distinguish species, genera, and

Higher groups

Biochemistry

Nature of cellular components such as cell wall, RNA

Molecules, ribosomes, storage inclusions, pigments, antigens;

Biochemical tests

Distinguish species, genera, and

Higher groups

Genetics

Percentage of DNA bases (G + C ratio); DNA hybridization

Determine relatedness within

Genera and families

Serology

Slide agglutination, fluorescent-labelled antibodies

Distinguish strains and some

Species

Phage typing

Susceptibility to a group of bacteriophages

Identification and distinguishing

Of strains

Sequence of bases in

rRNA

rRNA sequencing

Determine relatedness among

All living things

Protein profiles

Separate proteins by two-dimensional PAGE (electrophoresis)

Distinguish strains

Economic Importance

Metabolic product

For large scale production of desired product

Pathogenesis

Symptoms of abnormality

Prevention and cure of disease

Chapter 2 Gram negative spiral and curved rods(Spirocheats Spirillum Azospirillum Bdellovibrio Desulfovibrio)

SpirocheatsSpirillumAzospirillumBdellovibrioDesulfovibrio

Spirocheats

Domain:      Bacteria

Phylum:      Spirochaetes

Class:          Spirochaetia

Order.         Spirochaetales

The class contains spirochetes in one order, Spirochaetales, which is presently comprised of four families, namely Spirochaetaceae,               Brachyspiraceae, Brevinemataceae, and Leptospiraceae.

Key to the genera of the family Spirochaetaceae

Family Spirochaetaceae

Genus I. Spirochaeta

Habitat

Indigenous to aquatic freshwater and marine environments such as the sediments, mud and water of ponds, marshes, swamps, lakes, rivers, and hot springs.Occur commonly in H2S-containing environments.Free-living.None reported to be pathogenic.

Morphology

Spirochetes are Gram-stain-negative.Cells are 0.2–75 µm in diameter and 5–250 µm in length.Spirochaeta cells are helically shaped and possess the typical ultrastructural features of spirochetes.Under unfavourable conditions, spherical cells or structures 0.5–2.0 µm (occasionally up to 10 µm) in diameter are formed.The outermost structure of the cells is an“outer membrane,”or outer sheath,”which encloses the coiled cell body (“protoplasmic cylinder”) consisting of the cytoplasm, the nuclear region, and the peptidoglycan-cytoplasmic membrane complex.Organelles ultrastructurally similar to bacterial flagella are located in the area between the outer membrane and the protoplasmic cylinder. These organelles are essential components of the motility apparatus of spirochetes are usually called “periplasmic flagella.”Other names used to designate these motility organelles are “periplasmic fibrils,”“axial fibrils,” “axial filaments,” and “endoflagella.”Cells translocate when suspended in liquids and crawl or creep when in contact with solid surfaces.The outermost broken line indicates the outer membrane (outer sheath).The protoplasmic cylinder is represented by the area delimited by the solid line adjacent to the outermost broken line. The cell has two periplasmic flagella indicated by the solid-dotted thin lines wound around the protoplasmic cylinder.The insertion points of the periplasmic flagella are represented by the small circles near the ends of the cell.

Physiology

Obligately anaerobic or facultatively anaerobic.Optimum temperature range, 25–68°C.Under aerobic growth conditions the facultatively anaerobic species usually produce carotenoid pigments that give a yellow, yellow-orange, or red coloration to colonies or cells in liquid media.Thermophilic species are known.Spirochaeta species are resistant to the antibiotic rifampicin (rifampin) at concentrations of 1–50 μg rifampicin/ml.Resistance to rifampicin may be due to low affinity of the spirochetal RNA polymerase for the antibiotic.

Growth &Nutrition

Chemo-organotrophic, using a variety of carbohydrates as carbon and energy sources.The main products of anaerobic carbohydrate metabolism are ethanol, acetate, CO2, and H2.Under anaerobic conditions, Spirochaeta stenostrepta, Spirochaeta litoralis, Spirochaeta aurantia, and Spirochaeta halophila ferment carbohydrates to pyruvate via the Embden–Meyerhof pathwayColonies of Spirochaeta diffuse or spread through the agar medium in which they are growing.This phenomenon is especially apparent in agar media containing low substrate concentrations and 1% or less agar.Diffusion of colonies is due to migration of the growing cells through the agar medium.Migration of the cells is the result of chemotaxis toward the growth substrate and of the ability of spirochetes to locomote through agar gelsThe growth of obligately anaerobic species of Spirochaeta is abundant in media with 1.0 or 1.5 g of agar/100 ml, whereas the growth of some strains of facultatively anaerobic species of Spirochaeta is inhibited in media containing more than 1.0% agar.However, these strains grow abundantly when the agar concentration in the medium is 1% or lower.A procedure in which the antibiotic rifampicin (rifamycin) serves as a selective agent is quite effective for the isolation of free-living (genus Spirochaeta) and host-associated (genus Treponema) spirochetes from natural environments.This procedure is based on the observation that spirochetes in general are naturally resistant to rifampicin

Genetics

Many not-yet-cultivated species identified as based on 16S rRNA gene sequence comparisons.Not considered as pathogenic. The DNA G+C content is 45–66 mol%.

Importance &/or Pathogenesis

Cellulose degradation by Clostridium thermocellum is enhanced in the presence of Spirochaeta caldaria, a thermophilic spirochete from a freshwater hot spring.Possibly, species of Spirochaeta might be employed in processes for the direct bioconversion of cellulose-containing wastes to fuels such as H2 or ethanol.

Examples

Spirochaeta plicatilis,Spirochaeta Africana, Spirochaeta americanaSpirochaeta asiatica, Spirochaeta halophila

Genus II. Borrelia

Habitat

All known Borrelia species have an inherent requirement for a competent (often genospeciesspecific) arthropod vector and vector-suitable mammalian host(s) to be maintained in their natural enzootic cyclesThree types of arthropod vectors have been associated with transmission of Borrelia: the human body louse, the argasid or soft tick, and the ixodid or hard tick.Numerous mammalian hosts appear to be involved in maintaining Borrelia within a population, with the primary reservoir usually being a small mammal.

Morphology

Helical cells are 0.2–0.5 µm by 3–30 µm, composed of 3–10 loose coils.The cells are surrounded by a surface layer, an outer membrane, periplasmic flagella, and a protoplasmic cylinder.The cells are actively motile with frequent reversal of the direction of translational movement.Gram-stain-negative.Stain well with Giemsa stain.

Physiology

Species which have been grown in vitro are microaerophilic.Growth &NutritionBorrelia are unable to elongate or beta-oxidize fatty acids.The fastidious nature of this organism and the requirement for serum supplemented mammalian tissue culture medium.Analysis of the metabolic pathways identified suggests that glucose serves as the major energy source

Genetics

The DNA G+G content of a limited number of species is 27–32 mol%

Importance &/or Pathogenesis

The causative agents of tick-borne Lyme disease and relapsing fever and louse-borne relapsing fever in man.

Examples

3 human-pathogenic species Borrelia burgdorferi, Borrelia afzelii, and Borrelia garinii 7 other species that are minimally pathogenic or nonpathogenic: Borrelia japonica, Borrelia lusitaniae, Borrelia tanukii, Borrelia turdi, Borrelia sinica, Borrelia, and Borrelia valaisiana.

Genus III. Cristispira

Habitat

Cristispira develops especially dense populations in and on the crystalline style of many marine (and a few freshwater) mollusks.Styles are noncellular, gelatinous, cellulase-containing rods that extend into the stomach of many bivalve mollusks.All are obligate symbionts in the digestive system of molluscs or arthropods.The habitats of these organisms are predictable (e.g., the crystalline style of bivalve molluscs for Cristispira and the intestine of dry wood eating cockroaches and termites for the others).

Morphology

Helical cells are 0.5–3.0 µm in diameter × 30–180 µm in length, displaying 2–10 helical turns.Ends of cells are blunt, rounded, or tapered. Round inclusions of unknown composition or function are seen in stained preparations or under phase microscopy.Multiple cytoplasmic vesicles bounded by a double membrane are observed in electron microscopy thin sections.Gram-negative, motile

Physiology

In suspension, cells remain motile longer at 5–10°C than at temperatures above 20°.Glucosone inhibits motilityMotility occurs under aerobic and putative anaerobic conditions.May be microaerophilic.A suspension of a high concentration of Cristispira on a microscope slide will form a distinct zone, a ring, of cells near the edge of a cover slip with no cells present in the centre of the slide.Cells typically lyse in distilled waterCells survive, and perhaps have limited growth, in media with proteinaceous substrates and fructose.

Growth &Nutrition

Not grown in pure culture.

Genetics

The DNA G+C content is not known

Importance &/or Pathogenesis

Not known to be pathogenic and probably represent normal microflora.

Examples

Cristispira pectinis

Genus IV. Treponema

Habitat

Found in the oral cavity, intestinal tract, and genital areas of humans and animals.Some species are pathogenic.Also found in the hindgut of termites

Morphology

Host-associated, helical cells 0.1–0.7 μm in diameter and 1–20 μm in length.Cells have tight regular or irregular spirals and one or more periplasmic flagella (axial fibrils or axial filaments) inserted at each end of the protoplasmic cylinder.Cytoplasmic filaments are seen in the protoplasmic cylinder just under the cytoplasmic membrane and running parallel with the periplasmic flagella.Under unfavourable cultural or environmental conditions, spherical cells are formed.The organisms stain poorly with the usual aniline dyes; however, those that are capable of aniline-dye uptake are Gram negative.Staining can best be accomplished by the use of silver impregnation or immunofluorescent methods.Gram-stain-negative.

Physiology

Cells have rotational movement in liquid media, and translational motion in media with high viscosity [e.g., those containing 1% (w/v) methyl cellulose].In a semisolid or solid medium, cells exhibit a serpentine type movement, sometimes referred to as creeping motility.Strictly anaerobic or microaerophilic.

Growth &Nutrition

Chemo-organotrophs, using a variety of carbohydrates or amino acids for carbon and energy sources.None of the pathogenic Treponema has been cultivated continuously in artificial media or in tissue culture.Cultivated anaerobic species are catalase- and oxidase-negative.The cultivable Treponemas can be isolated by two general methods.The first uses membrane filters placed on the surface of agar media.The second method uses rifampicin as a selective agent.The non-cultivatable, pathogenic Treponema species can be propagated through animal inoculation.

Genetics

Many not-yet-cultivated species identified as based on 16S rRNA gene sequence comparisons.The DNA G+C content is 36–54 mol%Importance &/or PathogenesisIn syphilis, Treponema pallidum multiplies locally and causes a characteristic painless, ulcerative lesion called a“chancre.”ExamplesTreponema amylovorum, Treponema pallidum, Treponema azotonutricium, Treponema carateum, Treponema denticola(oral cavity of humans)

Family Brachyspiraceae