spore | Definition, Types, & Examples | japancarnews.info
Spores are agents of asexual reproduction, whereas gametes are agents of sexual reproduction. Spores are produced by bacteria, fungi, algae, and plants. Keywords: microbes, microbial response, mechanisms of biocide action, microbial resistance The fungi and algae (except euglenoids) possess rigid cell walls, outgrowing and vegetative forms produced from spores themselves. .. being the most relevant in relation to reduced susceptibility to biocides. Organisms in the Domain Bacteria lack membrane-bound organelles such as the the Eubacteria) and blue-green bacteria (the blue-green algae when I was a . Endospores allow bacteria that produce them to survive in the harshest of Possible symbiosis of bacteria within early eukaryotic cells was a major step in the.
Most of the structural proteins found in the cell wall are glycosylated and contain mannosethus these proteins are called mannoproteins or mannans. The inclusion of additional polysaccharides in algal cells walls is used as a feature for algal taxonomy. They form microfibrils in the cell walls of a number of marine green algae including those from the generaCodiumDasycladusand Acetabularia as well as in the walls of some red algaelike Porphyra and Bangia.
It is a common polysaccharide in the cell walls of brown algae. They occur in the cell walls of most algae; those common in red algae include agarosecarrageenanporphyranfurcelleran and funoran. Other compounds that may accumulate in algal cell walls include sporopollenin and calcium ions. The group of algae known as the diatoms synthesize their cell walls also known as frustules or valves from silicic acid.
Until recently they were widely believed to be fungi, but structural and molecular evidence  has led to their reclassification as heterokontsrelated to autotrophic brown algae and diatoms. Unlike fungi, oomycetes typically possess cell walls of cellulose and glucans rather than chitin, although some genera such as Achlya and Saprolegnia do have chitin in their walls. Slime molds[ edit ] The dictyostelids are another group formerly classified among the fungi. They are slime molds that feed as unicellular amoebaebut aggregate into a reproductive stalk and sporangium under certain conditions.
Cells of the reproductive stalk, as well as the spores formed at the apex, possess a cellulose wall. The cell envelope comprises a plasma membraneseen here in light brown, and a thick peptidoglycan -containing cell wall the purple layer. No outer lipid membrane is present, as would be the case in gram-negative bacteria. The red layer, known as the capsuleis distinct from the cell envelope. Cell envelope and Bacterial cell structure Around the outside of the cell membrane is the bacterial cell wall.
Bacterial cell walls are made of peptidoglycan also called mureinwhich is made from polysaccharide chains cross-linked by unusual peptides containing D- amino acids. The cell wall is essential to the survival of many bacteria, although L-form bacteria can be produced in the laboratory that lack a cell wall.
There are broadly speaking two different types of cell wall in bacteria, called gram-positive and gram-negative. The names originate from the reaction of cells to the Gram staina test long-employed for the classification of bacterial species. In contrast, gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins.
Whereas peptidoglycan is a standard component of all bacterial cell walls, all archaeal cell walls lack peptidoglycan with the exception of one group of methanogens. One type of archaeal cell wall is that composed of pseudopeptidoglycan also called pseudomurein.
This type of wall is found in some methanogenssuch as Methanobacterium and Methanothermus.
Microbes and the human body – Antibiotics
Like the peptidoglycan found in bacterial cell walls, pseudopeptidoglycan consists of polymer chains of glycan cross-linked by short peptide connections. Additionally, the cross-linking peptides are L-amino acids rather than D-amino acids as they are in bacteria.
This type of cell wall is composed entirely of a thick layer of polysaccharideswhich may be sulfated in the case of Halococcus. Many different types of microorganism bacteria, fungi and protozoa have been associated with serious human infections.
Certain filamentous algae may produce thick carpet-like mats in freshwaters. Algal growth causes problems in swimming pools and cooling towers, and their control by algicides is often necessary. There are obviously considerable differences in the structure and composition of microbial cells and Table 1 summarizes the chemical nature of the outer layers of some of these organisms.
There is no consistent theme. There are variations between similar types of organisms, e. Further, variations in chemical composition may occur on growth under different conditions producing altered responses to antimicrobial agents. It is not surprising, therefore, that microbial susceptibilities to biocides and especially to antibiotics differ greatly. For example, many antibiotics that specifically interfere with the 70S ribosome function in bacteria will also inhibit protein synthesis in mitochondria and chloroplasts.
Fusidic acid has some activity against a range of protozoa, including Giardia lamblia. Mupirocin is active at low concentrations against staphylococci but has some clinical effect at much higher concentrations against fungi, and chloramphenicol shows a broad spectrum of activity against actinomycetes, mycoplasmas, Leptospira species and Treponema pallidum.
Chlorhexidine salts CHXquaternary ammonium compounds QACsmonoaldehydes formaldehydedialdehydes [glutaraldehyde GTAortho-phthalaldehyde OPA ], chlorine-releasing agents CRAs and other halogens, organomercurials, phenolics, peroxygens and alcohols all show varying degrees of activity against bacteria, bacterial spores, fungi, viruses and protozoa 1 and at least some have algicidal activity.
Similarities and differences in response, based upon cellular physiology and structure, form the basis of this review. The likely outcomes of biocidal action in practice are thereby not covered, although one particular and important aspect, namely biofilm cultures, will be referred to when necessary.
Whilst the actions of biocides on viruses and bacteriophages will not be discussed in detail, it is necessary to consider these effects when appropriate insofar as they shed light on the nature of the interaction between biocides and a particular target site, e.
There are some general questions that need to be posed when biocidal activity is considered against different types of microbes: These and other aspects are discussed below. Biocide adsorption and uptake into cells Interaction of a biocide with the whole microbial cell is conventionally measured by determining its adsorption.
As a result, five different classes of adsorption are known. For example, the Z adsorption pattern is shown by phenoxyethanol and Escherichia coli but not Pseudomonas aeruginosa and Candida lipolyica. The initial stages followed the H high affinity pattern, indicative of a high affinity of iodine for substrates. Thereafter, the shape varied, depending upon the iodine system solution or iodophor and the substrate type of cells.Lesson 5: Eukaryotes, Helminths, Fungi, Algae, Lichens and Viruses
Biocides and antibiotics must traverse the outer cell layer s to reach their target sites, usually present within microbial cells Figure 1. The information as to how this uptake is achieved is somewhat limited. Figure 2 shows the general pattern of entry of a biocide into microbial cells. These biofilms and mats can range from a few micrometres in thickness to up to half a metre in depth, and may contain multiple species of bacteria, protists and archaea.
Bacteria living in biofilms display a complex arrangement of cells and extracellular components, forming secondary structures, such as microcoloniesthrough which there are networks of channels to enable better diffusion of nutrients.
Intracellular structures The bacterial cell is surrounded by a cell membrane which is made primarily of phospholipids. This membrane encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. The general lack of internal membranes in bacteria means these reactions, such as electron transportoccur across the cell membrane between the cytoplasm and the outside of the cell or periplasm.
Scale bars indicate nm. Most bacteria do not have a membrane-bound nucleus, and their genetic material is typically a single circular bacterial chromosome of DNA located in the cytoplasm in an irregularly shaped body called the nucleoid. Like all living organismsbacteria contain ribosomes for the production of proteins, but the structure of the bacterial ribosome is different from that of eukaryotes and Archaea. Cell envelope Around the outside of the cell membrane is the cell wall.
Bacterial cell walls are made of peptidoglycan also called mureinwhich is made from polysaccharide chains cross-linked by peptides containing D- amino acids.