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[DESCRIPTION]
Several methods have been presented by Adams (1959) to determine adsorption kinetics of bacteriophages. One way to measure the adsorption efficiency of cyanophages is to assay for free unadsorbed phages (Suttle and Chan 1993). The principle of this assay is to add a known quantity of viruses to host cells (e.g., at an MOI = 0.01 to 0.1). Over a period of 1 to 2 h, small subsamples of the virus:host solution are removed ca. every 15 min and diluted 100-fold to stop further adsorption. The host is then separated from free viruses by centrifugation, and the number of free viruses remaining in the supernatant determined by plaque or end-point dilution assays. A plot of the abundance of free viruses remaining in solution as a function of time should produce a straight line. The slope of this line is then used to calculate the adsorption rate.<br /><br />This procedure can be adapted for other host–virus systems. The example given is for host BBC1 and cyanophage BBC1-P1 (Suttle and Chan 1993).

[BEFORE_START]
Because of the short sampling intervals, it is very important to have everything ready before you begin. Having media equilibrated to the appropriate temperature, pre-labeled agar plates and tubes, tables to record the time etc will facilitate acquisition of better data.

[GUIDELINES]
The first step in the life cycle of a virus is adsorption to host cells. If the virus does not adsorb to a viable host, infection will not take place. Where bacteriophage adsorption rates are often in the order of minutes, cyanophages usually adsorb to their host cells at a much slower rate; and not all contacts result in an infection. Suttle and Chan (1993) found that it took 45 min for 80% of cyanophage BBC1-P1 to be adsorbed to its host. Some factors that can affect adsorption rates are (1) host abundance (a minimum of 104 cells per mL are needed to have a sufficiently high rate of adsorption); (2) physiological state of the host (which could affect the availability of receptor sites); (3) physical environment (temperature, viscosity); (4) chemical environment (ions, salts, co-factors); (5) light (adsorption rate is light dependent in some species (Clokie et al. 2006); and (6) host strain. If every contact results in an infection, this would have tremendous ecological impact. Understanding how these factors affect the rate of virus adsorption would help one design better experiments, interpret data, and construct better models for virus-host cell relationships.<br /><br />Under constant environmental and cultural conditions of the host cell, the rate of adsorption can be described using the following equation: <br /><br /><strong>K = 2.3/(B)t x log (p<sub>0</sub>/p)</strong><br /><br />where B = concentration of cyanobacteria (cells mL<sup>-1</sup>), p<sub>0</sub> = phage assayed at time zero, p = phage not adsorbed at time t (min), K is the velocity constant (ml min<sup>-1</sup>).<br /><br />
<table width="717">
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<td width="564"><strong>Table 1.</strong> Suggested table for recording sampling times and details for adsorption kinetics experiments.
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<td width="84">Time point (minutes)</td>
<td width="59">Replicate</td>
<td width="109">Time: subsampled from tube</td>
<td width="72">Time:centrifuged</td>
<td width="81">Time: tube placed on ice</td>
<td width="96">Time: added to plating cells</td>
<td width="61">Volume titered</td>
<td width="83">Results: # of PFUs</td>
<td width="69">Average # of PFUs</td>
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<tr>
<td width="84">T=0</td>
<td width="59">    A</td>
<td width="109"> </td>
<td width="72"> </td>
<td width="81"> </td>
<td width="96"> </td>
<td width="61"> </td>
<td width="83"> </td>
<td rowspan="3" width="69"> </td>
</tr>
<tr>
<td width="84">Â </td>
<td width="59">    B</td>
<td width="109"> </td>
<td width="72"> </td>
<td width="81"> </td>
<td width="96"> </td>
<td width="61"> </td>
<td width="83"> </td>
</tr>
<tr>
<td width="84">Â </td>
<td width="59">    C</td>
<td width="109"> </td>
<td width="72"> </td>
<td width="81"> </td>
<td width="96"> </td>
<td width="61"> </td>
<td width="83"> </td>
</tr>
<tr>
<td width="84">T=15</td>
<td width="59">    A</td>
<td width="109"> </td>
<td width="72"> </td>
<td width="81"> </td>
<td width="96"> </td>
<td width="61"> </td>
<td width="83"> </td>
<td rowspan="3" width="69"> </td>
</tr>
<tr>
<td width="84">Â </td>
<td width="59">    B</td>
<td width="109"> </td>
<td width="72"> </td>
<td width="81"> </td>
<td width="96"> </td>
<td width="61"> </td>
<td width="83"> </td>
</tr>
<tr>
<td width="84">Â </td>
<td width="59">    C</td>
<td width="109"> </td>
<td width="72"> </td>
<td width="81"> </td>
<td width="96"> </td>
<td width="61"> </td>
<td width="83"> </td>
</tr>
<tr>
<td width="84">Etc.</td>
<td width="59"> </td>
<td width="109"> </td>
<td width="72"> </td>
<td width="81"> </td>
<td width="96"> </td>
<td width="61"> </td>
<td width="83"> </td>
<td width="69"> </td>
</tr>
</tbody>
</table>
</td>
</tr>
</tbody>
</table>

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