Difference Between Gram Positive And Gram Negative Bacteria In Tabular Form Pdf
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- Gram positive and Gram negative bacteria differ in their sensitivity to cold plasma
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- Differences between Gram Positive and Gram Negative Bacteria
Multiple responses of gram-positive and gram-negative bacteria to mixture of hydrocarbons. Most of our knowledge about pollutants and the way they are biodegraded in the environment has previously been shaped by laboratory studies using hydrocarbon-degrading bacterial strains isolated from polluted sites. In present study Gram-positive Mycobacterium s p.
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However, the exact mode of action is still being explored. Here we report that CAP efficacy is directly correlated to bacterial cell wall thickness in several species. Biofilms of Gram positive Bacillus subtilis , possessing a In contrast, biofilms of Gram negative Pseudomonas aeruginosa , possessing only a 2. Planktonic cultures of Gram negative Pseudomonas libanensis also had a higher log 10 reduction than Gram positive Staphylococcus epidermidis. Mixed species biofilms of P. However, when grown in co-culture, Gram negative P.
Emission spectra indicated OH and O, capable of structural cell wall bond breakage, were present in the plasma. This study indicates that cell wall thickness correlates with CAP inactivation times of bacteria, but cell membranes and biofilm matrix are also likely to play a role. Plasma is ionized gas and can be generated using a range of gases, including argon, helium, nitrogen and compressed air.
Plasma contains radicals, excited molecules, charged particles and UV photons. Cold atmospheric plasma CAP is active towards a broad spectrum of microorganisms. There is an active debate about which plasma species are responsible for microbial inactivation, with reactive oxygen, hydrogen peroxide H 2 O 2 and UV photons the most likely candidates 1 , 2 , 3 , 4. Many studies have tested the antibacterial activity of CAP in vitro , but only very limited data on clinical trials have been reported to date 5 , 6.
It appears that the antimicrobial efficiency of CAP depends on specific properties of the devices used, making it challenging to investigate the mode of action. It has a DC power supply and can be used with a range of rare gases.
A number of studies have shown its antibacterial effectiveness 10 , Cold plasma is hypothesised to have different targets within the cell, including cell membrane and cell wall, DNA and intracellular proteins 4 , Plasma species were shown to be able to break important bonds in the cell wall peptidoglycan structure in Gram positive bacteria 13 , 14 as well as leading to membrane lipid peroxidation in Gram negative bacteria This disruption of the outer shell of the cell will lead to leakage of cellular components, including potassium, nucleic acid and proteins.
After the cell wall is broken, reactive species can penetrate into the interior of the cell and further damage DNA and intracellular protein from oxidative or nitrosative species In bacteria, the Gram stain provides an important classification system, as several cell properties can be correlated with the cell envelope. These differences in the cell envelope confer different properties to the cell, in particular responses to external stresses, including heat, UV radiation and antibiotics.
Most in vitro studies focus on investigating plasma mediated killing of laboratory-cultured single-species planktonic cells. However, this does not resemble the natural conditions of bacterial existence. The vast majority of bacteria live in aggregates attached to a surface in often multi-species biofilms.
Bacterial biofilms cause problems in several industries by colonizing factory equipment and contaminating products. They are also a major contributor to human infections and are particularly hard to eradicate with antibiotic therapy.
Biofilms promote bacterial survival in the environment, as they coordinate group behaviour, enhance metabolic interactions, enhance gene transfer, produce a protective exopolysaccharide matrix from the cells and increase antibiotic resistance 16 , 17 , 18 , 19 , Here we show that cold-plasma-induced bacterial biofilm killing is correlated with the thickness of the bacterial cell wall, but additional factors are involved in determining sensitivity to CAP inactivation.
Using a commercially-available plasma source, a much higher reduction in cell numbers is achieved for Gram negative bacteria than Gram positive bacteria, independent of planktonic or biofilm mode of growth. Moreover, clinically-relevant P. This has implications for eradicating environmental biofilms and treating clinical significant infections, in which bacteria are known to often occur as multispecies communities. Strains had single attached cells and small microcolonies were beginning to form.
Only isolated dead red cells were observed with the majority being green viable cells. All biofilms were tested for inactivation rates using the kINPen med operated with argon gas Fig. A similarly high reduction was observed for P. For B. The error bars represent standard deviations for 3 biofilm samples. A profound difference of CFU log 10 reductions after CAP treatment was observed between Gram positive and Gram negative species biofilms, prompting us to investigate a possible correlation of CAP inactivation rates with cell wall dimensions.
Values of cell wall thickness were sourced from previous studies. For P. The cell wall thickness of E. No indication of cell wall thickness measurements or high resolution TEM images were found for P.
In natural habitats, bacteria often occur in mixed-species communities instead of mono-species cultures. One example is the co-occurrence of P. To investigate whether CAP can eradicate mixed-species biofilms in a similar fashion to single species, co-cultures of P. As for single-species biofilms, P. However, the final CFU log 10 reduction was only 2.
Interestingly, S. Mixed biofilms of P. After treatment, cells were scraped from the coupon and dilutions plated onto Pseudomonas agar P. To evaluate whether species-dependent inactivation occurs only during biofilm mode of growth, the Gram positive S. A similar response compared to biofilm treatment was observed. Overnight cultures of P. After treatment, cells were scraped from the coupon and dilutions plated onto nutrient agar. The error bars represent standard deviations for 3 samples.
Emission spectra were measured to examine any qualitative changes in plasma characteristics during the treatment time. A slight decrease of intensity of metastable Ar emission was observed Fig. We have observed a marked difference in sensitivity to CAP treatment between Gram positive and Gram negative bacterial biofilms.
The visible biofilm biomass appears similar among the six different species, with all showing a layer of single cells and small microcolonies before treatment Fig. The similar thickness and structure of the biofilms suggests that factors other than biofilm architecture are responsible for the observed variation in CAP sensitivity. The major difference between the two groups of bacteria is the thickness of the cell wall and the presence of an outer membrane in Gram negative bacteria only.
The main component of the cell wall is peptidoglycan, which is found in almost all bacteria and is responsible for preserving the integrity of the cell. Destruction of peptidoglycan either through mutations or external stresses e. The organism with the thickest cell wall, B. However, a correlation within the Gram groups could not be seen. For example, the Gram negative E.
The bacterial cytoplasmic membrane consists of phospholipids and the Gram negative outer membrane consists of phospholipids and lipopolysaccharides Peroxidation of lipids is a well-known mechanism of CAP inactivation 4 , Membrane lipids have been suggested to be the macromolecules of the cell that are most vulnerable to physical stresses due to their position at the outside of the cell envelope and their sensitivity to ROS In addition, due to the presence of pore-forming proteins porins , the outer membrane is leakier than the cytoplasmic membrane and the cell wall and thus potentially easier to penetrate by CAP, possibly leading to a higher sensitivity of Gram negative bacteria to plasma treatment.
In agreement with our observation of higher sensitivity of Gram negative cells to CAP, Laroussi et al. The study suggested that the observed cell lysis of E. Lysis may occur when the outer membrane has acquired a sufficient electrostatic charge that the outward electrostatic stress exceeds its tensile strength 34 , Moreover, a higher surface roughness or irregularity due to the presence of an outer membrane could render Gram negative cells more sensitive to electrostatic disruption This suggests that additional factors to cell wall thickness play a role in CAP sensitivity.
A study by Montie et al. However, the diffusion across a thick Gram positive cell wall would presumably still be slower than across a thin Gram negative cell wall, leading to a difference in CAP sensitivity. In contrast, a study by Mozetic et al. Interestingly, by being operated in an open-air environment, the emission intensity of atomic oxygen and hydroxyl radicals increased without external supply of oxygen.
In contrast, a slight decrease in intensity of metastable Ar emission was observed. Argon was used as the feeding gas for the plasma equipment. Oxygen and water vapour can originate from the surrounding air or from the sample being treated.
The increase in atomic oxygen and hydroxyl radical density may be due to evaporation from the samples being treated. The decrease in emission intensity is likely a consequence of the efficient quenching of argon metastables by oxygen molecules and atoms Yusupov et al. It was shown that plasma species can break structurally-important bonds of peptidoglycan, ultimately leading to cell death In some bacteria the cell wall has additional structural elements that could also influence CAP sensitivity.
For example, B. In addition to the structural envelope of single cells, the extracellular matrix ECM in which biofilm cells are embedded is likely to affect CAP sensitivity. The ECM gives cells added protection to external stress. The ECM composition varies between species, but it consists mainly of extracellular polymeric substance, including polysaccharides, lipids, proteins and nucleic acids It has been suggested that the ECM composition plays an important role in susceptibility to reactive species, such as found in CAP 40 ,
Gram positive and Gram negative bacteria differ in their sensitivity to cold plasma
It is important to note that not all bacteria have a cell wall. The two different cell wall types can be identified in the lab by a differential stain known as the Gram stain. Originally, it was not known why the Gram stain allowed for such reliable separation of bacterial into two groups. Once the electron microscope was invented in the s, it was found that the staining difference correlated with differences in the cell walls. Here is a website that shows the actual steps of the Gram stain. After this stain technique is applied the gram positive bacteria will stain purple, while the gram negative bacteria will stain pink. A cell wall, not just of bacteria but for all organisms, is found outside of the cell membrane.
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The Gram stain is the most widely used staining procedure in bacteriology.
Differences between Gram Positive and Gram Negative Bacteria
Metrics details. The highest proportion of susceptible A. Vancomycin-resistant VR isolates represented 1. Highest percentages of VR. Isolates were collected from patients with an infectious disease and identified as the causative agent according to laboratory criteria.
Gram Positive Cell walls
Prokaryotes are identified as gram-positive if they have a multiple layer matrix of peptidoglycan forming the cell wall. Crystal violet, the primary stain of the Gram stain procedure, is readily retained and stabilized within this matrix, causing gram-positive prokaryotes to appear purple under a brightfield microscope after Gram staining. For many years, the retention of Gram stain was one of the main criteria used to classify prokaryotes, even though some prokaryotes did not readily stain with either the primary or secondary stains used in the Gram stain procedure. Microbiologists currently recognize two distinct groups of gram-positive, or weakly staining gram-positive, prokaryotes. The name Actinobacteria comes from the Greek words for rays and small rod , but Actinobacteria are very diverse. Their microscopic appearance can range from thin filamentous branching rods to coccobacilli. Some Actinobacteria are very large and complex, whereas others are among the smallest independently living organisms.
Retain crystal violet dye and stain blue or purple. Can be decolorized to accept counterstain safranin and stain pink or red 2 Cell Wall Cell Wall is nm thick. Cell Wall is nm thick. The wall is wavy. Why not in gram -ve? What is the reason that inhibition by basic dyes, susceptibility to anionic detergents and resistance to sodium azide is low in gram negative while high in gram positive bacteria? Why are Gram-positive has 2 rings in basal body and Gram-negative 4 rings in basal body?
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