scholarly journals Stress-induced formation of cell wall-deficient cells in filamentous actinomycetes

2016 ◽  
Author(s):  
K. Ramijan ◽  
E. Ultee ◽  
J. Willemse ◽  
A.J. Wondergem ◽  
D. Heinrich ◽  
...  
Keyword(s):  
Cell Wall ◽  
Prolonged Exposure ◽  
Gene Clusters ◽  
Adaptation Strategy ◽  
Hyperosmotic Stress ◽  
Cell Type ◽  
Biosynthetic Gene Clusters ◽  
Resistance Determinants ◽  
A Cell ◽  
Almost All

ABSTRACTThe cell wall is a shape-defining structure that envelopes almost all bacteria. One of its main functions is to serve as a protection barrier to environmental stresses. Bacteria can be forced in a cell wall-deficient state under highly specialized conditions, which are invariably aimed at interrupting cell wall synthesis. Therefore, the relevance of such cells has remained obscure. Here we show that many filamentous actinomycetes have a natural ability to generate a new, cell wall-deficient cell type in response to hyperosmotic stress, which we call S-cells. This wall-deficient state is transient, as S-cells are able to switch to the canonical mycelial mode-of-growth. Remarkably, prolonged exposure of S-cells to hyperosmotic stress yielded variants that are able to proliferate indefinitely without their cell wall. This is the first report that demonstrates the formation of wall-deficient cells as a natural adaptation strategy and their potential transition into stable wall-less forms solely caused by prolonged exposure to osmotic stress. Given that actinomycetes are potent antibiotic producers, our work also provides important insights into how biosynthetic gene clusters and resistance determinants may disseminate into the environment.

Future directions for the discovery of antibiotics from actinomycete bacteria

2017 ◽  
Vol 1 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Rebecca Devine ◽  
Matthew I. Hutchings ◽  
Neil A. Holmes
Keyword(s):  
New Technologies ◽  
Gene Clusters ◽  
Biosynthetic Gene Clusters ◽  
Future Directions ◽  
Streptomyces Species ◽  
Genus Streptomyces ◽  
New Antibiotics ◽  
The Uk ◽  
Almost All ◽  
New Generation

Antimicrobial resistance (AMR) is a growing societal problem, and without new anti-infective drugs, the UK government-commissioned O'Neil report has predicted that infectious disease will claim the lives of an additional 10 million people a year worldwide by 2050. Almost all the antibiotics currently in clinical use are derived from the secondary metabolites of a group of filamentous soil bacteria called actinomycetes, most notably in the genus Streptomyces. Unfortunately, the discovery of these strains and their natural products (NPs) peaked in the 1950s and was then largely abandoned, partly due to the repeated rediscovery of known strains and compounds. Attention turned instead to rational target-based drug design, but this was largely unsuccessful and few new antibiotics have made it to clinic in the last 60 years. In the early 2000s, however, genome sequencing of the first Streptomyces species reinvigorated interest in NP discovery because it revealed the presence of numerous cryptic NP biosynthetic gene clusters that are not expressed in the laboratory. Here, we describe how the use of new technologies, including improved culture-dependent and -independent techniques, combined with searching underexplored environments, promises to identify a new generation of NP antibiotics from actinomycete bacteria.

scholarly journals The AWA1 Gene Is Required for the Foam-Forming Phenotype and Cell Surface Hydrophobicity of Sake Yeast

2002 ◽  
Vol 68 (4) ◽  
pp. 2018-2025 ◽  
Author(s):  
Hitoshi Shimoi ◽  
Kazutoshi Sakamoto ◽  
Masaki Okuda ◽  
Ratchanee Atthi ◽  
Kazuhiro Iwashita ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Repetitive Sequences ◽  
Alcoholic Beverage ◽  
Cell Surface Hydrophobicity ◽  
Surface Hydrophobicity ◽  
A Cell ◽  
Characteristic Sequences ◽  
Foam Forming ◽  
Almost All

ABSTRACT Sake, a traditional alcoholic beverage in Japan, is brewed with sake yeasts, which are classified as Saccharomyces cerevisiae. Almost all sake yeasts form a thick foam layer on sake mash during the fermentation process because of their cell surface hydrophobicity, which increases the cells' affinity for bubbles. To reduce the amount of foam, nonfoaming mutants were bred from foaming sake yeasts. Nonfoaming mutants have hydrophilic cell surfaces and no affinity for bubbles. We have cloned a gene from a foam-forming sake yeast that confers foaming ability to a nonfoaming mutant. This gene was named AWA1 and structures of the gene and its product were analyzed. The N- and C-terminal regions of Awa1p have the characteristic sequences of a glycosylphosphatidylinositol anchor protein. The entire protein is rich in serine and threonine residues and has a lot of repetitive sequences. These results suggest that Awa1p is localized in the cell wall. This was confirmed by immunofluorescence microscopy and Western blotting analysis using hemagglutinin-tagged Awa1p. Moreover, an awa1 disruptant of sake yeast was hydrophilic and showed a nonfoaming phenotype in sake mash. We conclude that Awa1p is a cell wall protein and is required for the foam-forming phenotype and the cell surface hydrophobicity of sake yeast.

scholarly journals Use of Permanent Wall-Deficient Cells as a System for the Discovery of New-to-Nature Metabolites

2020 ◽  
Vol 8 (12) ◽  
pp. 1897
Author(s):  
Shraddha Shitut ◽  
Güniz Özer Bergman ◽  
Alexander Kros ◽  
Daniel E. Rozen ◽  
Dennis Claessen
Keyword(s):  
Cell Wall ◽  
Secondary Metabolites ◽  
Gene Clusters ◽  
Chemical Diversity ◽  
Biosynthetic Gene Clusters ◽  
Microbial Cell Factories ◽  
Cell Factories ◽  
Genome Recombination ◽  
Antibiotic Discovery ◽  
Insight Into

Filamentous actinobacteria are widely used as microbial cell factories to produce valuable secondary metabolites, including the vast majority of clinically relevant antimicrobial compounds. Secondary metabolites are typically encoded by large biosynthetic gene clusters, which allow for a modular approach to generating diverse compounds through recombination. Protoplast fusion is a popular method for whole genome recombination that uses fusion of cells that are transiently wall-deficient. This process has been applied for both inter- and intraspecies recombination. An important limiting step in obtaining diverse recombinants from fused protoplasts is regeneration of the cell wall, because this forces the chromosomes from different parental lines to segregate, thereby preventing further recombination. Recently, several labs have gained insight into wall-deficient bacteria that have the ability to proliferate without their cell wall, known as L-forms. Unlike protoplasts, L-forms can stably maintain multiple chromosomes over many division cycles. Fusion of such L-forms would potentially allow cells to express genes from both parental genomes while also extending the time for recombination, both of which can contribute to an increased chemical diversity. Here, we present a perspective on how L-form fusion has the potential to become a platform for novel compound discovery and may thus help to overcome the antibiotic discovery void.

The Cell's Biological Rods and Ropes

MRS Bulletin ◽  
1999 ◽  
Vol 24 (10) ◽  
pp. 27-31 ◽  
Author(s):  
David Boal
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Chemical Composition ◽  
Intermediate Filaments ◽  
Plant Cells ◽  
Cell Type ◽  
Animal Cells ◽  
Limited Variation ◽  
A Cell ◽  
Mechanical Elements

Despite a variety of shapes and sizes, the generic mechanical structure of cells is remarkably similar from one cell type to the next. All cells are bounded by a plasma membrane, a fluid sheet that controls the passage of materials into and out of the cell. Plant cells and bacteria reinforce this membrane with a cell wall, permitting the cell to operate at an elevated osmotic pressure. Simple cells, such as the bacterium shown in Figure 1a, possess a fairly homogeneous interior containing the cell's genetic blueprint and protein workhorses, but no mechanical elements. In contrast, as can be seen in Figure 1b, plant and animal cells contain internal compartments and a filamentous cytoskeleton—a network of biological ropes, cables, and poles that helps maintain the cell's shape and organize its contents.Four principal types of filaments are found in the cytoskeleton: spectrin, actin, microtubules, and a family of intermediate filaments. Not all filaments are present in all cells. The chemical composition of the filaments shows only limited variation from one cell to another, even in organisms as diverse as humans and yeasts. Membranes have a more variable composition, consisting of a bi-layer of dual-chain lipid molecules in which are embedded various proteins and frequently a moderate concentration of cholesterol. The similarity of the cell's mechanical elements in chemical composition and physical characteristics encourages us to search for universal strategies that have developed in nature for the engineering specifications of the cell. In this article, we concentrate on the cytoskeleton and its filaments.

scholarly journals A MORPHOLOGICAL STUDY OF HALOBACTERIUM HALOBIUM AND ITS LYSIS IN MEDIA OF LOW SALT CONCENTRATION

1967 ◽  
Vol 34 (1) ◽  
pp. 365-393 ◽  
Author(s):  
Walther Stoeckenius ◽  
Robert Rowen
Keyword(s):  
Cell Wall ◽  
Cell Membrane ◽  
Salt Concentration ◽  
Prolonged Exposure ◽  
Structural Characteristics ◽  
Wall Material ◽  
Breakdown Product ◽  
Distilled Water ◽  
Fixation Techniques ◽  
A Cell

The reported absence of a cell wall in halobacteria cannot be confirmed. Improved fixation techniques clearly show a cell wall-like structure on the surface of these cells. A stepwise reduction of the salt concentration causes the release of cell wall material before the cell membrane begins to disintegrate. The cell membrane breaks up into fragments of variable but rather small size, which are clearly different from a 4S component reported by others to be the major breakdown product of the cell membrane. It appears more likely that the 4S component arises from the dissolution of the cell wall. A residue of large membranous sheets remains even after prolonged exposure of halobacteria envelopes to distilled water. The lipids in these sheets do not differ significantly from the lipids in the lysed part of the cell membrane. The sheets, however, contain a purple-colored substance, which is not present in the lysed part. The easily sedimentable residue that remains after lysis of the cells or envelopes in distilled water also contains "intracytoplasmic membranes" with unusual structural characteristics. They can also be identified in sections through intact bacteria or envelope preparations. Their function is at present unknown but seems to be related to the formation of gas vacuoles in these organisms.

scholarly journals Formation of wall-less cells in Kitasatospora viridifaciens requires cytoskeletal protein FilP in oxygen-limiting conditions

2020 ◽  
Author(s):  
Eveline Ultee ◽  
Ariane Briegel ◽  
Dennis Claessen
Keyword(s):  
Cell Wall ◽  
Prolonged Exposure ◽  
Electron Tomography ◽  
Cell Formation ◽  
Normal Growth ◽  
Cytoskeletal Proteins ◽  
Hyperosmotic Stress ◽  
Wall Material ◽  
Bacterial Survival ◽  
Cell Extrusion

ABSTRACTThe cell wall is considered an essential component for bacterial survival, providing structural support and protection from environmental insults. Under normal growth conditions, filamentous actinobacteria insert new cell wall material at the hyphal tips regulated by the coordinated activity of cytoskeletal proteins and cell wall biosynthetic enzymes. Despite the importance of the cell wall, some filamentous actinobacteria can produce wall-deficient S-cells upon prolonged exposure to hyperosmotic stress. Here we performed cryo-electron tomography and live cell imaging to further characterize S-cell extrusion in Kitasatospora viridifaciens. We show that exposure to hyperosmotic stress leads to DNA compaction, membrane and S-cell extrusion and thinning of the cell wall at hyphal tips. Additionally, we find that the extrusion of S-cells is abolished in a cytoskeletal mutant strain that lacks the intermediate filament-like protein FilP. Furthermore, micro-aerobic culturing promotes the formation of S-cells in the wild-type, but the limited oxygen still impedes S-cell formation in the ΔfilP mutant. These results demonstrate that S-cell formation is stimulated by oxygen-limiting conditions and dependent on the presence of an intact cytoskeleton.

scholarly journals Heterogeneity and Cell Type-Specific Localization of a Cell Wall Glycoprotein from Carrot Suspension Cells

1991 ◽  
Vol 96 (3) ◽  
pp. 705-712 ◽  
Author(s):  
Fred A. van Engelen ◽  
Peter Sterk ◽  
Hilbert Booij ◽  
Jan H.G. Cordewener ◽  
Wim Rook ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Type ◽  
Suspension Cells ◽  
Specific Localization ◽  
A Cell ◽  
Cell Type Specific

Dendritic cells of the human epidermis: immuno-electron microscopic studies of la antigen reactivity

1978 ◽  
Vol 36 (2) ◽  
pp. 644-645
Author(s):  
G. Rowden ◽  
M. G. Lewis ◽  
T. M. Phillips
Keyword(s):  
Dendritic Cells ◽  
Langerhans Cells ◽  
Cell Types ◽  
Cell Type ◽  
Electron Microscopic ◽  
La Antigen ◽  
Microscopic Studies ◽  
A Cell ◽  
C3 Receptors ◽  
Antigen Reactivity

Langerhans cells of mammalian stratified squamous epithelial have proven to be an enigma since their discovery in 1868. These dendritic suprabasal cells have been considered as related to melanocytes either as effete cells, or as post divisional products. Although grafting experiments seemed to demonstrate the independence of the cell types, much confusion still exists. The presence in the epidermis of a cell type with morphological features seemingly shared by melanocytes and Langerhans cells has been especially troublesome. This so called "indeterminate", or " -dendritic cell" lacks both Langerhans cells granules and melanosomes, yet it is clearly not a keratinocyte. Suggestions have been made that it is related to either Langerhans cells or melanocyte. Recent studies have unequivocally demonstrated that Langerhans cells are independent cells with immune function. They display Fc and C3 receptors on their surface as well as la (immune region associated) antigens.

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