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Bacteria ( Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory.[10] The study of bacteria is known as bacteriology, a branch of microbiology. Etymology Origin and early evolution Morphology Many bacterial species exist simply as single cells, others associate in characteristic patterns: Neisseria form diploids (pairs), Streptococcus form chains, and Staphylococcus group together in "bunch of grapes" clusters. Even more complex morphological changes are sometimes possible. Cellular structure Structure and contents of a typical gram-positive bacterial cell (seen by the fact that only one cell membrane is present). Intracellular structures The bacterial cell is surrounded by a cell membrane (also known as a lipid, cytoplasmic or plasma membrane). Many important biochemical reactions, such as energy generation, use concentration gradients across membranes. Extracellular structures Endospores Growth and reproduction Related:  MICROBIOLOGYThe Biology of Life

Archaea The Archaea ( Archaea were initially classified as bacteria, receiving the name archaebacteria (or Kingdom Monera), but this classification is outdated.[1] Archaeal cells have unique properties separating them from the other two domains of life: Bacteria and Eukaryota. The Archaea are further divided into four recognized phyla. Classification is difficult, because the majority have not been studied in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment. Classification[edit] New domain[edit] Current classification[edit] The classification of archaea, and of prokaryotes in general, is a rapidly moving and contentious field. A superphylum - TACK - has been proposed that includes the Aigarchaeota, Crenarchaeota, Korarchaeota and Thaumarchaeota.[18] This superphylum may be related to the origin of eukaryotes. Species[edit] The classification of archaea into species is also controversial. Origin and evolution[edit] R.S. Morphology[edit]

Cell nucleus HeLa cells stained for the cell nucleus DNA with the BlueHoechst dye. The central and rightmost cell are in interphase, thus their entire nuclei are labeled. On the left, a cell is going through mitosis and its DNA has condensed. Because the nuclear membrane is impermeable to large molecules, nuclear pores are required that regulate nuclear transport of molecules across the envelope. History[edit] Between 1877 and 1878, Oscar Hertwig published several studies on the fertilization of sea urchin eggs, showing that the nucleus of the sperm enters the oocyte and fuses with its nucleus. Structures[edit] Nuclear envelope and pores[edit] Nuclear pores, which provide aqueous channels through the envelope, are composed of multiple proteins, collectively referred to as nucleoporins. Nuclear lamina[edit] The nuclear lamina is composed mostly of lamin proteins. Mutations in lamin genes leading to defects in filament assembly are known as laminopathies. Chromosomes[edit] Nucleolus[edit]

Prokaryote Cell structure of a bacterium , one of the two domains of prokaryotic life. The division to prokaryotes and eukaryotes reflects two distinct levels of cellular organization rather than biological classification of species. Prokaryotes include two major classification domains: the bacteria and the archaea . Archaea were recognized as a domain of life in 1990. These organisms were originally thought to live only in inhospitable conditions such as extremes of temperature , pH , and radiation but have since been found in all types of habitats . [ edit ] Relationship to eukaryotes The division to prokaryotes and eukaryotes is usually considered the most important distinction among organisms. Prokaryotes lack distinct mitochondria and chloroplasts . In 1977, Carl Woese proposed dividing prokaryotes into the Bacteria and Archaea (originally Eubacteria and Archaebacteria) because of the major differences in the structure and genetics between the two groups of organisms. [ edit ] Sociality Nanobe

Eukaryote Eukaryotes can reproduce both asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two genetically identical cells. In meiosis, DNA replication is followed by two rounds of cell division to produce four daughter cells each with half the number of chromosomes as the original parent cell (haploid cells). Cell features[edit] Eukaryotic cells are typically much larger than those of prokaryotes. Internal membrane[edit] Detail of the endomembrane system and its components A 3D rendering of an animal cell cut in half. The nucleus is surrounded by a double membrane (commonly referred to as a nuclear membrane or nuclear envelope), with pores that allow material to move in and out. Vesicles may be specialized for various purposes. Mitochondria and plastids[edit] Simplified structure of a mitochondrion Plants and various groups of algae also have plastids. Cytoskeletal structures[edit] Cell wall[edit] Differences among eukaryotic cells[edit]

Biofilm IUPAC definition Aggregate of microorganisms in which cells that are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS) adhere to each other and/or to a surface. Note 1: A biofilm is a fixed system that can be adapted internally to environmental conditions by its inhabitants. Note 2: The self-produced matrix of extracellular polymeric substance, which is also referred to as slime, is a polymeric conglomeration generally composed of extracellularbiopolymers in various structural forms.[1] Microbes form a biofilm in response to many factors, which may include cellular recognition of specific or non-specific attachment sites on a surface, nutritional cues, or in some cases, by exposure of planktonic cells to sub-inhibitory concentrations of antibiotics.[4][5] When a cell switches to the biofilm mode of growth, it undergoes a phenotypic shift in behavior in which large suites of genes are differentially regulated.[6] Formation[edit] Development[edit]

Mitochondrion Two mitochondria from mammalian lung tissue displaying their matrix and membranes as shown by electron microscopy History[edit] The first observations of intracellular structures that probably represent mitochondria were published in the 1840s.[13] Richard Altmann, in 1894, established them as cell organelles and called them "bioblasts".[13] The term "mitochondria" itself was coined by Carl Benda in 1898.[13] Leonor Michaelis discovered that Janus green can be used as a supravital stain for mitochondria in 1900. Friedrich Meves, in 1904, made the first recorded observation of mitochondria in plants (Nymphaea alba)[13][14] and in 1908, along with Claudius Regaud, suggested that they contain proteins and lipids. Benjamin F. In 1939, experiments using minced muscle cells demonstrated that one oxygen atom can form two adenosine triphosphate molecules, and, in 1941, the concept of phosphate bonds being a form of energy in cellular metabolism was developed by Fritz Albert Lipmann. Matrix[edit]

De la diversité au sein des bactéries La diversité est une des clés de de la résistance bactérienne aux antibiotiques. Une étude de l’université de Washington précise un mécanisme dans les cellules bactériennes qui est une clé de cette diversité. Un nouveau mode de diversification Lorsqu’elle se divise, une bactérie peut donner naissance à deux cellules qui possèdent le même génome mais pour lesquelles le partage des organites cellulaires n'a pas été équitable. C'est un autre moyen pour les cellules de se diversifier. C-di-GMP. Un mécanisme impliqué dans les infections nosocomiales Des tests ont prouvé que chez le bacille pyocyanique (bactérie fortement pathogène et difficile à traiter), les cellules ayant des niveaux élevés de c-di-GMP ont tendance à rester immobiles et à adhérer aux surfaces pour former des colonies.

Evolution of cells The first cells[edit] The origin of cells was the most important step in the evolution of life on Earth. The birth of the cell marked the passage from pre-biotic chemistry to partitioned units resembling modern cells. The final transition to living entities that fulfill all the definitions of modern cells depended on the ability to evolve effectively by natural selection. This transition has been called the Darwinian transition. If life is viewed from the point of view of replicator molecules, cells satisfy two fundamental conditions: protection from the outside environment and confinement of biochemical activity. Partitioning may have begun from cell-like spheroids formed by proteinoids, which are observed by heating amino acids with phosphoric acid as a catalyst. Another possibility is that the shores of the ancient coastal waters may have served as a mammoth laboratory, aiding in the countless experiments necessary to bring about the first cell. [edit] Canonical patterns[edit]

Microbiologie alimentaire Le rôle des microbes dans la fabrication des aliments De très nombreux produits alimentaires sont élaborés avec l'aide de microorganismes. Citons les yaourts (Lactobacillus bulgaricus, Streptococcus thermophilus, Bifidobacterium), les fromages (Lactococcus lactis, L. cremoris, Propionobacterium, Penicillium camemberti, P. roquerforti, etc.), les saucissons, les jambons, les viandes et les poissons fermentés (Bacillus halophiles), le vin, la bière et les autres diverses boissons fermentées alcoolisées (Saccharomyces, Botrytis cinerea), les vinaigres (Acetobacter, Gluconobacter), les pains (Saccharomyces, Lactobacillus), la choucroute (Leuconostoc mesenteroides, Leucobacillus plantarum), les produits d'ensilage pour les animaux (diverses espèces anaérobies), etc. Détérioration et décomposition des aliments Mais il arrive quelquefois que le développement de microorganismes sur des aliments ne se détectent ni visuellement, ni au goût. La conservation des aliments [Ouvrir les liens :