Scanning Electron Microscopy of Bacterial Colonies

Afrikian, E. G.; Julian, Grant St.; Bulla, Lee A.

doi:10.1128/aem.26.6.934-937.1973

Cited by 10 publications

(8 citation statements)

References 5 publications

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“…-: -. were in direct contact with the agar surface (1,3). However, in our hands N. gonorrhoeae type 4 did not form visible colonies when incubated for 22 h on Millipore or Nucleopore filters.…”

Section: Resultscontrasting

confidence: 49%

“…DISCUSSION By using scanning electron microscopy, several workers have attempted to observe bacterial colonies located on the agar surface. The result has often been discouraging, mainly because both colonies and agar are heavily distorted during the preparation procedure (1,23). To avoid such problems some investigators have inoculated bacteria on membrane filters (Millipore Corp.) or dialysis membrane strips that IS--l"', ;.,.…”

Section: Resultsmentioning

confidence: 99%

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Scanning electron microscopic study of virulent and avirulent colonies of Neisseria gonorrhoeae

Elmros¹,

Hörstedt²,

Winblad³

1975

Infect Immun

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A preparation procedure for scanning electron microscopy was developed by which gonococcal colonies can be studied directly on the agar surface. After glutaraldehyde fixation directly in petri dishes, small agar pieces were cut out and dehydrated stepwise in increasing concentrations of ethanol. The blocks were thereafter transferred to a critical-point drying apparatus, via steps of increased gradients up to 100% amyl acetate. By this method five different gonococcal colony types could be distinguished analogous to light microscopic observations made by others. At higher magnifications an abundance of intercellular strands was found between the cells in virulent type 1 and 2 colonies, but not in the avirulent types 3 through 5. These strands seemed to anchor the cells to each other and to the agar surface. The presence of such structures probably explains the highly convex surface of virulent colonies and explains why colonies of avirulent strains exhibit a radial extension and a flat upper surface. The nature of these filamentous intercellular strands is discussed.Morphological properties of bacterial colonies are of both practical and theoretical interest in many areas of microbiology. Despite this, relatively little is known about factors determining the shape of colonies.

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Section: Resultscontrasting

confidence: 49%

Section: Resultsmentioning

confidence: 99%

Scanning electron microscopic study of virulent and avirulent colonies of Neisseria gonorrhoeae

Elmros¹,

Hörstedt²,

Winblad³

1975

Infect Immun

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“…We determined the pH of water, using Metrohm Lab827 pH meter (Metrohm AG, Herisau, Switzerland) with a glass microelectric and a digital Lumiscope L2214 digital thermometer to measure temperature. Scanning electron microscope (SEM) was performed for E. coli of water sample …”

Section: Methodsmentioning

confidence: 99%

Deactivation of Escherichia coli with different volumes in drinking water using cold atmospheric plasma

Asadollahfardi

Khandan

Aria

2019

Contributions to Plasma Physics

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This experimental study aimed to evaluate the potential of cold atmospheric plasma jet to deactivate Escherichia coli from drinking water. We studied the effect of the volume of water samples on the performance of plasma jet on deactivation of E. coli of 1, 500, 1,000, 1,500, and 2,000 cubic centimetres. The results of deactivation of E. coli in 500 and 1,000 cc water samples were the same as one cc of a water sample and we observed 8-log reduction of E. coli using 50 W. In 1,500 and 2,000 cc water samples at 8 min using a power of 50 W, 4.5 and 2.9 log reduction of E. coli was achieved and while we used 20 W, 2.5 and 1.8 log reduction of E. coli bacteria was performed. This indicated that the increasing volume of water above 1,500 cc caused the reduction of the efficiency of E. coli removal. Also, increasing power caused to increase E. coli removal efficiency. In addition, we monitored changes in pH values and temperature during experiments. Using 20 W, the temperature was increased (natural temperature of the water was 22 • C) 2 • C after 8 min while applying 50 W, the temperatures were raised 5 • C. pH of the water after 8 min in the 1,000 cc water sample, with an input power of 20 W, decreased from 7.1 to 5.5; while the input power was 50 W, pH changed from 7.1 to 4.3. With an increase in plasma irradiation time, the number of E. coli had a significant decrease per min while using in samples of 1 cc. After 8 min, we observed 4-log reductions of E. coli with the input power of 20 W and 8-log reduction of bacteria with the input power of 50 W. In 1,500 and 2,000 cc of water samples using plasma radiation for 8 min, 2.5 log and 1.8 log reduction of E. coli was achieved, respectively. This means that an increasing volume of water above 1,500 cc needs more power and time to deactivate E. coli from the water.

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“…Field-of-view (FOV) dimensions accessible by SEM enable capturing statistically significant numbers of resolved individual cells within a single image [Figures S1−S2 in the Supporting Information (SI)]. 18,19 The high spatial resolution and depth-of-field of SEM also enable simultaneous observation of μm-scale objects, such as bacteria, and NPs resolved individually or in aggregates ( Figure 1).…”

mentioning

confidence: 99%

Analytical Protocols for Separation and Electron Microscopy of Nanoparticles Interacting with Bacterial Cells

et al. 2015

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An important step toward understanding interactions between nanoparticles (NPs) and bacteria is the ability to directly observe NPs interacting with bacterial cells. NP-bacteria mixtures typical in nanomedicine, however, are not yet amendable for direct imaging in solution. Instead, evidence of NP-cell interactions must be preserved in derivative (usually dried) samples to be subsequently revealed in high-resolution images, for example, via scanning electron microscopy (SEM). Here, this concept is realized for a mixed suspension of model NPs and Staphylococcus aureus bacteria. First, protocols for analyzing the relative colloidal stabilities of NPs and bacteria are developed and validated based on systematic centrifugation and comparison of colony forming unit (CFU) counting and optical density (OD) measurements. Rate-dependence of centrifugation efficiency for each component suggests differential sedimentation at a specific predicted rate as an effective method for removing free NPs after co-incubation; the remaining fraction comprises bacteria with any associated NPs and can be examined, for example, by SEM, for evidence of NP-bacteria interactions. These analytical protocols, validated by systematic control experiments and high-resolution SEM imaging, should be generally applicable for investigating NP-bacteria interactions.

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Scanning Electron Microscopy of Bacterial Colonies

Cited by 10 publications

References 5 publications

Scanning electron microscopic study of virulent and avirulent colonies of Neisseria gonorrhoeae

Scanning electron microscopic study of virulent and avirulent colonies of Neisseria gonorrhoeae

Deactivation of Escherichia coli with different volumes in drinking water using cold atmospheric plasma

Analytical Protocols for Separation and Electron Microscopy of Nanoparticles Interacting with Bacterial Cells

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