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Phages

Phages are visible only after lysis of their host cells. Lysis can be performed either in liquid culture or on agar plates, the latter giving a better view on plaque morphology, uniformity and purity of the respective phage. Therefore, we recommend to perform lysis on plates whenever possible. Furthermore, counting plaques by performing dilution series gives the phage titre of a suspension (pfu = plaque forming units). DSMZ delivers only high-titre phage suspensions that are generally centrifuged and filtrated and therefore free of bacterial cells. Please, use the phage suspension as soon as possible, store away an original aliquot at 4°C and do not freeze phage suspensions without using a cryoprotectant like glycerol. Generally, DSMZ only guarantees a positive lysis when the recommended suitable host strain is used. Please, observe additional information sheets delivered along with some of our phages in order to fulfil special requirements. When performing lysis in liquid culture, the lysis procedure should be observed as it happens that a clear lysed culture is overgrown by developing resistant mutants. Great care has to be taken regarding clean work, locally separated from laboratory benches for bacterial culturing. Some phages are highly infective and transmissible even by air drifts. If contamination of a phage suspension occurs, single-plaque isolation can be performed.

Please click here for the list of phages.

Please note: If phages are sent abroad as suspensions on special request, the order is without reclamation rights.

Additional information:

Supply, storage and propagation of phages (PDF, 19 KB) resp. in German: Abgabe, Aufbewahrung und Vermehrung von Phagen (PDF, 21 KB)
Revitalisation of Vacuum-Dried Phages (see below)
FAQs (see below)

Revitalisation of Vacuum-Dried Bacteriophages

Several bacteriophages of our DSMZ collection are delivered as lyophilised phage suspensions on filter paper: a tested high-titre suspension of the respective phage had been vacuum-dried on filter paper and checked for viability after this drying process. We only deliver lyophilised phages with high viability and tested survival rates.

For revitalisation of the vacuum-dried phages, please observe the following steps:

For revitalisation of the vacuum-dried phages, please observe the following steps:

Prepare an agar plate with the appropriate phage host and recommended medium by plating the host using either soft agar (0.75% agar medium) as an upper layer or a plated liquid layer (usually 0.1 mL) of host suspension so that the host plate is ready to use for lysis. Please, use ONLY the recommended media (liquid and solid) and buffers. Do NOT pre-incubate the host without phage. Host and phage will be incubated TOGETHER (see below).
Open the ampoule of the phage acc. to the procedure as described for our bacterial cultures (DSMZ homepage or yellow information sheet for recipients of cultures). Take out the filter paper (contains the phage suspension), place it in the middle of the host plate
Add 0.1 mL of appropriate medium on the filter paper, incubate this plate with phage and host as described for the host, usually overnight. Alternatively, start incubation of the host/phage system in the morning and observe the plates until lysis occurs
Lysis leads to a clear zone around the filter paper. There are several phages causing turbid plaques and therefore also a turbid zone around the filter paper. In case this agar plate is foreseen for preparing a phage stock solution, the filter paper can be removed and phages resolved by using appropriate recommended buffer or medium in order to get a phage stock suspension.
Alternatively to the lysis on solid agar medium, lysis may be performed in liquid culture by adding the filter paper directly into a small exponentially growing fresh host culture, followed by further incubating phage and host together. Observe this culture until lysis occurs. A frequently observed disadvantage of lysis in liquid culture is that phage-resistant bacterial mutants arise and overgrow the culture so that the lysis effect is not visible anymore. Therefore, we recommend to carefully observe the lysis process. The advantage of lysis in liquid culture may be a high phage titre.
The phage suspension harvested after the above point 4 can be used for further purification or phage propagation steps. Suspensions of most phages store well at 4°C for one or two weeks or longer periods. DSMZ does not guarantee a long-term survival of phages while stored in the customer’s laboratory. All biological material delivered by DSMZ is for immediate use only. Please, see DSMZ’s Terms and Conditions information.
For saving and propagating the phages on agar plates and in liquid culture, you might cut the filter paper in two pieces and proceed with the above steps 2 and 5 in parallel.

General information on phages is given on our homepage, phage-specific information is given in the respective catalogue information. Please, carefully read all specific information before working with our phages.

DSMZ, June 2006

FAQs

Does an order on a phage include its host, are phage and host delivered together?

No, phage and host have to be mentioned separately on the order, they are different order positions.

In what form will the phage be delivered, dried or liquid?

Orders within Germany: with the exception of MS2 (DSM 13767) and Qß (DSM 13768) all other phages are usually supplied as suspensions at ambient temperature. Orders outside Germany: phages are generally supplied filter-dried. Special agreements with DSMZ are possible.

How do I know the titre of a phage suspension supplied by DSMZ?

Phage suspensions supplied by DSMZ have checked and documented high titres of 108/mL – 1011/mL (pfu).

Can phage suspensions be stored in the refrigerator?

Most phages store well in the refrigerator for some weeks but DSMZ generally recommends immediate use, see Terms and Conditions.

Does a phage plate only on the host strain recommended by DSMZ?

Host spectra of phages are not tested by DSMZ so that successful lysis is only guaranteed for the phage/host system used and approved by DSMZ.

What is the difference between dried bacterial strains and filter-dried phages?

Bacterial cell suspensions are dried together with a protectant and a pellet forms that can be rehydrated, phages are dried as suspensions on filter paper strips.

Does the DSMZ “Opening of Ampoules and Rehydration of Dried Cultures” scheme apply to the revitalisation of dried phages supplied in glass ampoules?

No, see procedure “Revitalisation of Vacuum-Dried Phages” above