The Biology of Bacteria

2019 ◽  
Author(s):  
Armine Sefton
Keyword(s):  
Cell Wall ◽  
Bacterial Infections ◽  
Genetic Material ◽  
Gram Positive ◽  
Dna And Rna ◽  
Gram Staining ◽  
Genetic Features ◽  
Potential Pathogen ◽  
A Cell ◽  
Micro Organisms

Bacterial infections and infestations of man can be caused by both microbes and non-microbes. Microbes include bacteria, viruses, fungi, and protozoa. Non-microbes include worms, insects, and arachnids. This chapter concentrates on the basic biology of bacteria. A pathogen is an organism that is able to cause disease in its host and the pathogenicity of any organism is its ability to produce disease. Microbes express their pathogenicity by means of their virulence. The virulence of any pathogen is determined by any of its structural, biochemical, or genetic features that enable it to cause disease in the host. The relationship between a host and a potential pathogen is non- static; the likelihood of any pathogen causing disease in its host depends both on the virulence of the pathogen and the degree of resistance or susceptibility of the host, due mainly to the effectiveness of the host’s defence mechanisms. Two of the main factors influencing a bacteria’s pathogenicity are its ability to invade and it ability to produce toxins—either exotoxins or endotoxins. Bacteria are unicellular prokaryotic micro-organisms, unlike human cells, which are eukaryotic. Fungi, protozoa, helminths, and arthropods are also eukaryotic. Prokaryotic organisms contain both DNA and RNA, but their genetic material exists unbound in the cytoplasm of the cell as, unlike eukaryotic cells, they have no nuclear membrane. Sometimes bacteria contain additional smaller circular DNA molecules, called plasmids. The main features of a bacterium are the cell wall, cytoplasm, and cell membrane. However, some bacteria have additional features such as spores, capsules, fimbriae (pili), and flagellae. The construction of the cell wall is different in different bacteria, but all cell walls contain peptidoglycan. The structure of the cell wall determines the staining characteristics when stained using the Gram stain. Although its first use was over a hundred and fifty years ago, is still the standard method for primary classification of bacteria. Occasionally, bacteria do not have a cell wall. Gram staining of a fixed smear of bacteria is used to separate bacteria into Gram positive or Gram negative, and also to demonstrate their shape. Bacteria with a thick peptidoglycan layer but with no outer membrane stain purple and are called Gram positive.

scholarly journals L-Ficolin Specifically Binds to Lipoteichoic Acid, a Cell Wall Constituent of Gram-Positive Bacteria, and Activates the Lectin Pathway of Complement

2004 ◽  
Vol 172 (2) ◽  
pp. 1198-1202 ◽  
Author(s):  
Nicholas J. Lynch ◽  
Silke Roscher ◽  
Thomas Hartung ◽  
Siegfried Morath ◽  
Misao Matsushita ◽  
...  
Keyword(s):  
Cell Wall ◽  
Lipoteichoic Acid ◽  
Lectin Pathway ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Cell Wall Constituent ◽  
A Cell

scholarly journals Methods for Confirming the Gram Reaction of Gram-variable Bacillus Species Isolated from Tobacco

2000 ◽  
Vol 19 (2) ◽  
pp. 97-101
Author(s):  
A Morin ◽  
N Poirier ◽  
S Vallee ◽  
A Porter
Keyword(s):  
Cell Wall ◽  
Bacillus Species ◽  
Gram Negative Bacteria ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria ◽  
A Cell ◽  
Staining Techniques ◽  
Susceptibility Tests ◽  
Hydrolysis Of

AbstractBacillusis a predominant genus of bacteria isolated from tobacco. The Gram stain is the most commonly used and most important of all diagnostic staining techniques in microbiology. In order to help confirm the Gram positivity ofBacillusisolates from tobacco, three methods using the chemical differences of the cell wall and membrane of Gram-positive and Gram-negative bacteria were investigated: the KOH (potassium hydroxide), the LANA (L-alanine-4-nitroanilide), and the vancomycin susceptibility tests. When colonies of Gram-negative bacteria are treated with 3% KOH solution, a slimy suspension is produced, probably due to destruction of the cell wall and liberation of deoxyribonucleic acid (DNA). Gram-positive cell walls resist KOH treatment. The LANA test reveals the presence of a cell wall aminopeptidase that hydrolyzes the L-alanine-4-nitroanilide in Gram-negative bacteria. This enzyme is absent in Gram-positive bacteria. Vancomycin is a glycopeptide antibiotic inhibiting the cell wall peptido-glycan synthesis of Gram-positive microorganisms. Absence of lysis with KOH, absence of hydrolysis of LANA, and susceptibility to vancomycin were used with the Gram reaction to confirm the Gram positivity of variousBacillusspecies isolated from tobacco.B. laevolacticusexcepted, all Bacillus species tested showed negative reactions to KOH and LANA tests, and all species were susceptible to vancomycin (5 and 30 µg).

scholarly journals Enzymes and Mechanisms Employed by Tailed Bacteriophages to Breach the Bacterial Cell Barriers

Viruses ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 396 ◽  
Author(s):  
Sofia Fernandes ◽  
Carlos São-José
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Bacterial Cell ◽  
Cell Envelope ◽  
Genetic Material ◽  
Cell Types ◽  
Virus Multiplication ◽  
Virus Particles ◽  
Bacterial Cell Envelope ◽  
A Cell

Monoderm bacteria possess a cell envelope made of a cytoplasmic membrane and a cell wall, whereas diderm bacteria have and extra lipid layer, the outer membrane, covering the cell wall. Both cell types can also produce extracellular protective coats composed of polymeric substances like, for example, polysaccharidic capsules. Many of these structures form a tight physical barrier impenetrable by phage virus particles. Tailed phages evolved strategies/functions to overcome the different layers of the bacterial cell envelope, first to deliver the genetic material to the host cell cytoplasm for virus multiplication, and then to release the virion offspring at the end of the reproductive cycle. There is however a major difference between these two crucial steps of the phage infection cycle: virus entry cannot compromise cell viability, whereas effective virion progeny release requires host cell lysis. Here we present an overview of the viral structures, key protein players and mechanisms underlying phage DNA entry to bacteria, and then escape of the newly-formed virus particles from infected hosts. Understanding the biological context and mode of action of the phage-derived enzymes that compromise the bacterial cell envelope may provide valuable information for their application as antimicrobials.

scholarly journals Novel Mechanism of Antibiotic Resistance Originating in Vancomycin-Intermediate Staphylococcus aureus

2006 ◽  
Vol 50 (2) ◽  
pp. 428-438 ◽  
Author(s):  
Longzhu Cui ◽  
Akira Iwamoto ◽  
Jian-Qi Lian ◽  
Hui-min Neoh ◽  
Toshiki Maruyama ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Antibiotic Resistance ◽  
Bacterial Infections ◽  
Cytoplasmic Membrane ◽  
Resistance Mechanism ◽  
Wall Thickening ◽  
Gram Positive ◽  
Peptidoglycan Biosynthesis ◽  
Significant Public Health

ABSTRACT As an aggressive pathogen, Staphylococcus aureus poses a significant public health threat and is becoming increasingly resistant to currently available antibiotics, including vancomycin, the drug of last resort for gram-positive bacterial infections. S. aureus with intermediate levels of resistance to vancomycin (vancomycin-intermediate S. aureus [VISA]) was first identified in 1996. The resistance mechanism of VISA, however, has not yet been clarified. We have previously shown that cell wall thickening is a common feature of VISA, and we have proposed that a thickened cell wall is a phenotypic determinant for vancomycin resistance in VISA (L. Cui, X. Ma, K. Sato, et al., J. Clin. Microbiol. 41:5-14, 2003). Here we show the occurrence of an anomalous diffusion of vancomycin through the VISA cell wall, which is caused by clogging of the cell wall with vancomycin itself. A series of experiments demonstrates that the thickened cell wall of VISA could protect ongoing peptidoglycan biosynthesis in the cytoplasmic membrane from vancomycin inhibition, allowing the cells to continue producing nascent cell wall peptidoglycan and thus making the cells resistant to vancomycin. We conclude that the cooperative effect of the clogging and cell wall thickening enables VISA to prevent vancomycin from reaching its true target in the cytoplasmic membrane, exhibiting a new class of antibiotic resistance in gram-positive pathogens.

scholarly journals Bacillus cereus from refulgent corneal ulcer: A case report

2021 ◽  
Vol 7 (3) ◽  
pp. 215-218
Author(s):  
Supriya Meshram ◽  
Prashant Khartade
Keyword(s):  
Corneal Ulcer ◽  
Agar Medium ◽  
Acute Onset ◽  
Ocular Infection ◽  
Gram Positive ◽  
Eye Infections ◽  
Gram Staining ◽  
Antibiotic Susceptibility Test ◽  
Potential Pathogen ◽  
History Of

A Gram-positive spore forming bacilli, aerobe or facultative anaerobe is . It is ubiquitous which disperse in the environment. is a potential pathogen accountable for fulminant human infectious disease and hardly ever contribute to eye infections. A 35-year-old farmer came to ophthalmology OPD on February 2019, and the patient complained of acute onset left eye pain with diminution of vision. There was history of eye injury by the vegetation (thorn). There was presence of corneal ulcer. The patient was not immunocompromised.Corneal scrapping was collected from left eye. On Gram staining from corneal scrapping only two Gram positive bacilli, with occasional pus cell and fibrinous exudate was seen. Culture on blood agar medium it showed beta haemolytic, about 2-5 mm in diameter, big flat, irregular edges and greyish white colonies which were oval, slightly granular but not dry. On Mac -Conkey agar medium it showed non lactose fermenting, big flat, irregular colonies.From colonies Gram staining showed Gram positive bacilli with spore. They were motile, catalase positive, oxidase positive, reduced nitrate to nitrite and were resistant to penicillin. The identification was also confirmed by Vitek. This case highlights the importance of cultivation, detection and antibiotic susceptibility test rather than treating patients with ocular infection empirically.

scholarly journals Histochemistry of the Gram-staining reaction for micro-organisms

1946 ◽  
Vol 133 (873) ◽  
pp. 391-406 ◽  
Keyword(s):  
Bile Salt ◽  
Ultra Violet ◽  
Sodium Cholate ◽  
Staining Reaction ◽  
Gram Positive ◽  
Large Measure ◽  
Gram Staining ◽  
Micro Organisms ◽  
Salt Extract ◽  
Positive Character

Extraction of certain Gram -positive micro-organisms with a 2% solution of a bile salt (preferably sodium cholate) strips the cell of an essential part of its dye-retaining constituent leaving a Gram-negative cytoskeleton. From the bile-salt extract there was separated a fraction which could be plated back on suitably reduced cytoskeletons and thereby restore in a large measure the Gram-positive character of the cell. The essential agent in the extract was magnesium ribonucleate, and it is considered that the Gram-positive or dye-retaining constituent is a nucleoprotein formed by the combination of ribonucleic acid with a basic protein in the cytoskeleton. The stripping and replating processes could be demonstrated by photomicrographs taken in ultra-violet light.

scholarly journals Ultrastructure and Peripheral Membranes of the Mycetomal Microorganisms of Sitophilus granarius (L.) (Coleoptera)

1966 ◽  
Vol 1 (2) ◽  
pp. 181-186
Author(s):  
I. GRINYER ◽  
A. J. MUSGRAVE
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Electron Microscope ◽  
Sitophilus Granarius ◽  
Large Numbers ◽  
A Cell ◽  
Intracellular Organelles ◽  
Micro Organisms

The peripheral membranes of the micro-organisms of the mycetocytes of adult midgut caecae and of larval mycetomes of Sitophilus granarius (L.), GG strain, have been examined with an electron microscope. The majority of the mycetocytes were depleted of intracellular organelles but contained large numbers of mycetomal micro-organisms, most of which exhibited only one peripheral membrane. Some mycetocytes, however, had well-developed ultrastructure and harboured mycetomal micro-organisms which showed two peripheral membranes, namely a cell wall and plasma membrane. Intermediate conditions also occurred. It is suggested that the absence of host-provided membranes around the micro-organisms categorizes them as obligate symbiotes.

Estimation of the State of the Bacterial Cell Wall by Fluorescent In Situ Hybridization

1998 ◽  
Vol 64 (8) ◽  
pp. 3059-3062 ◽  
Author(s):  
Elena Bidnenko ◽  
Carine Mercier ◽  
Josselyne Tremblay ◽  
Patrick Tailliez ◽  
Saulius Kulakauskas
Keyword(s):  
Cell Wall ◽  
In Situ Hybridization ◽  
Cell Walls ◽  
Fluorescent In Situ Hybridization ◽  
Cell Level ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
A Cell ◽  
Identification Of Bacteria

ABSTRACT Fluorescent in situ hybridization (FISH) is now a widely used method for identification of bacteria at the single-cell level. With gram-positive bacteria, the thick peptidoglycan layer of a cell wall presents a barrier for entry of horseradish peroxidase (HRP)-labeled probes. Therefore, such probes do not give any signal in FISH unless cells are first treated with enzymes which hydrolyze the peptidoglycan. We explored this feature of FISH to detect cells which have undergone permeabilization due to expression of autolytic enzymes. Our results indicate that FISH performed with HRP-labeled probes provides a sensitive method to estimate the states of cell walls of individual gram-positive bacteria.

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