Biofilms

Methods for Enzymatic Release of Microorganisms

Jean F. Brisou

• Publisher: CRC Press
• Year: 2017
• Print ISBN: 9781138557703
• eBook ISBN: 9781351368841
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

This text presents a new technique for detecting microorganisms, specifically bacteria found in all levels of the biosphere. It also discusses methods for enzymatic release of these microbes as well as their interactions in all ecosystems. Drawings and micrographs help to illustrate this concept.Part one is devoted to the mechanisms of adherence. The second part discusses microbial ecology and the bacterial population of tissues as well as both land and aquatic microbiocenoses in general. Part three specifically covers technique. What is known about the mechanisms of adherence justifies the choice of techniques suggested. Applications in areas such as nature, medicine, environmental hygiene and the food industry are discussed.The explanation of useful techniques, the author's research results, and practical application methods make this volume an essential reference tool for researchers, technicians and practitioners.

Part I
Adherence in Microbiology

1 Structures and Mechanisms

1. Defnition

As adherence of all microorganisms onto inert or living interfaces has been acknowledged for a long time, the mechanisms of it will be summarized by taking into account current data, using bacteria as an example. The framework of this essentially technical monograph does not justify developments concerning extremely complex biochemistry which would be more suitable for a "Treaty".

The process of adherence takes place schematically in three stages. The scenario is generally completed in 20 to 30 min in the optimal conditions of the environment. This is naturally not an absolute rule, simply a rough idea. The process takes place as follows:

1. Adsorption: Adsorption falls within the realm of physical chemistry. Ionic forces play a substantial role.
2. Adhesion: Adhesion is specific and characterized by a stereochemical molecular recognition, but it is a reversible process.
3. Adherence: Irreversible, terminal stage.

This conventional outline is sometimes criticized. It nevertheless has the advantage of being simple and didactic. What essentially stands out is that the two actors to be taken into account in this scenario are:

• The "Attached" (bacteria, for example)
• The "Attacher" (the living or inert host substrate)

Before analyzing these two fundamental components, a few concepts concerning cellular membranes which envelope bacteria as well as host tissues should be reviewed. All living cells are limited by a membrane that plays an important role in adherence phenomena.

2. Review of Membrane Structures

Numerous outlines published in various works (see bibliography) illustrate the complexity of membrane structures. Amphipolar molecules and phospholipids are superimposed in monomolecular layers. Certain internal asymmetries are responsible for variations in the distribution of electric charges and cause imbalances inducing the appearance of dipoles differentiated as instantaneous, permanent, or adipolar. All these elements obey the laws of Van der Waals, or are guided according to various modalities analyzed and debated by different authors. Invoking electrostatic forces, Keesen constructs singular associations and alignments; Debye, a partisan of electrostatic induction, is opposed to London, a partisan of electrokinetics and the action of apolar molecules.

This debate will be avoided by remembering that the Van der Waals type bonds, weaker than ionic covalents, are exceptions to the saturation phenomena and play an unquestionable role. This point will be dealt with later in the development of life processes. The interface phenomena that will be discussed later were perfectly analyzed in 1971 by Mazliak.⁹ The spatial congestion characterizing the chains of unsaturated fat acids is more substantial than that occupied by the saturated fat acids. The space included between these alignments facilitates the -CH₂ bonds and ensures the rigidity of the whole. A monomolecular film can thus be formed. The polar heads contract bonds with various cations, notably the bivalents Ca^f and Mg. They are united to remainders of P0₄H₃ themselves capable of belonging to two different but similar molecules. In this way, these bivalent cations ensure the bringing together of the polar heads and promote the organization of phospholipids in compact lamelar systems. Monovalent cations, such as Na⁺ or K⁺ only recognizing one molecule, cannot claim such unions.

2.1. Membrane Proteins

Membrane proteins are traditionally broken down into two groups: structural proteins and enzyme proteins intimately linked to the membranes.

2.1.1. Structural Proteins

Structural proteins are essentially hydrophobic — relatively unsoluble in a medium close to neutrality. Deprived of any enzymatic activity, they have the capacity of uniting with phospholipids and giving birth to complex compounds. In an alkaline medium, they associate to engender substances that sediment at low speed. In a neutral medium, the monomers aggregate and organize small-diameter fibrils. Mg⁺⁺ facilitates the development of the process; for example, myeline and fongic mitochondrias can be given as proof.

2.1.2. Enzyme Proteins

Due to the very substantial number of enzyme proteins, they cannot be counted here. A few examples are sufficient throughout this study to confirm the importance of these enzyme proteins. Along the way, adenosine triphosphatase, 5'nucleotidase, phosphatase glycerol, and other phosphatases, ribonuclease, numerous oxidoreductases, phospholipase A, etc. will be encountered.

2.2. Renewal of Membrane Constituents

The cellular membrane is the theater of considerable biochemical activity. It ensures that order is maintained in the heart of the cell. Life can be interpreted as a permanent reordering, a "neguentropy". Membrane structural molecules accomplish their mission based on their specific, catalytic, enzymatic potentialities, subjected to constant renewals. Mazliak wrote that "Everything happens, in the cells, as if masons were constantly replacing the bricks of the cell walls with new bricks, to make sure the walls are always new." This interpretation, full of imagery, shows the differences recorded between the cells depending on their age, their physiological condition, and the conditions of the environment in which microorganisms live.

Everyone knows that in optimal growth conditions a bacterial cell, in the strict sense of the term, 'becomes' and is transformed from one second to the next, giving birth to two daughter cells. In this life teeming with bacterial populations, only "snapshots" are taken. From one instant to the next, the antigenic patterns — the formation or disappearance of flagella — appear or disappear in function with the conditions of the medium. Wide variations in enzymatic activity are also observed, modifying the behavior of bacteria in general. Basic constituents can undergo completely unpredictable, profound reorganizations. Certain authors express all these modifications by diagrams that control their imagination. There are some twenty-odd models, many of which are inspired by Danielli's¹⁰ ideas, published between 1943 and 1956. Some invent micellar structures (Paysant et al.¹¹). Kavanau¹² attempts to make things clearer by limiting everything to two stable models, one of which was qualified as "open" and the other considered as "closed". Like an evolved chemical body, the membrane goes, depending on the circumstances and the constraints of the medium, from one configuration to another.

Cellular membranes, in all living beings, ensure the control of the movement of components of the microenvironment on the one hand and that of the intracellular substances on the other hand. Far from being passive, they recognize and sort everything that can enter in the cytoplasm and exit out of it. Pure and simple permeability does not obey the laws of physics, and in all but a few exceptions, the cell is alive; it reacts in every sense of the word, "... without transgressing the limits of what is possible" (F. Jacob).

We are thus led to the intimate, equally complex mechanisms of permeation. Nevertheless, certain metabolized substances obey the laws of diffusion of dissolved products depending on the gradient of concentration, but the speed of this diffusion is often slow. The highly selective character of the membrane with respect to mineral ions is also sufficiently known. It should simply be recalled that although these movements can go against the gradient of concentration, it is difficult to establish general laws based on them. It is sometimes possible to observe active transportation during which the ionic flow runs in the opposite direction of the concentration gradient, thus confirming the above. Such a phenomenon requires an additional expenditure of the cell's energy.

The breakdown of biopolymers is subjected to their spatial configuration, to their structure as much as to the ionic composition of the immediate environment, therefore to the breakdown of electric charges, which are never uniform nor continuous. Glycoproteins are, for example, always charged and intervene significantly in intercellular reactions, notably on the receptors assimilated to genuine biological signals of high specificity. The major role of such receptors dominates the development of adherence in all microorganisms, including viruses.

To sum things up, cellular membranes are composed of an assembly of intrinsic proteins located inside a lipidic layer and of extrinsic proteins emerging at the surface. The molecular orientation of each of the intrinsic proteins is specific to the species. Oligosides and monosaccharides form chains or unite together directly with certain proteins to give birth to glycoproteins or lipids. Other lipids form two quantitatively and qualitatively differe...

Table of contents

• Cover
• Title
• Copyright
• Contents
• Dedication
• INTRODUCTION
• PART I ADHERENCE IN MICROBIOLOGY
• PART II BACTERIA LIFE IN THE WILD
• PART III ENZYMATIC RELEASE TECHNIQUES OF BACTERIA
• POSTFACE
• BIBLIOGRAPHY
• INDEX