Question: How many bacteriophages are there per millilitre of seawater?
About the article "Virus", section "Bacterial viruses".

Candidate passages:
Bacteriophages are a common and diverse group of viruses and are the most abundant form of biological entity in aquatic environments – there are up to ten times more of these viruses in the oceans than there are bacteria, reaching levels of 250,000,000 bacteriophages per millilitre of seawater.
These viruses infect specific bacteria by binding to surface receptor molecules and then entering the cell.
Within a short amount of time, in some cases just minutes, bacterial polymerase starts translating viral mRNA into protein.
These proteins go on to become either new virions within the cell, helper proteins, which help assembly of new virions, or proteins involved in cell lysis.
Viral enzymes aid in the breakdown of the cell membrane, and, in the case of the T4 phage, in just over twenty minutes after injection over three hundred phages could be released.
The major way bacteria defend themselves from bacteriophages is by producing enzymes that destroy foreign DNA.
These enzymes, called restriction endonucleases, cut up the viral DNA that bacteriophages inject into bacterial cells.
Bacteria also contain a system that uses CRISPR sequences to retain fragments of the genomes of viruses that the bacteria have come into contact with in the past, which allows them to block the virus's replication through a form of RNA interference.
This genetic system provides bacteria with acquired immunity to infection.
ListShield is an Intralytix product that is applied to food for the prevention of listeriosis by killing strains of food-borne pathogenic "Listeria monocytogenes" bacteria.
Listeriosis is a serious disease with a high rate of mortality in susceptible individuals.
It is almost exclusively contracted by consuming contaminated food.
Since the "L. monocytogenes" bacteria are omnipresent in nature, even the most thorough hygiene concepts fail to guarantee that food products are free of listeria.
Bacteriophages are among the best studied organisms in the natural world.
This is because their molecular biology is relatively simple.
Many molecular principles were first studied in bacteriophages prior to being found in higher organisms.
Bacteriophages are ubiquitous.
High numbers can be found in seawater and also in fermented foods such as yogurt or cheese.
Bacteriophages are extremely specific in the bacteria they recognize.
The recognition is often limited to specific strains of one species, in rare cases several strains of the same species or genus are recognized.
With this fact in mind their potential in fighting unwanted bacteria has recently received increased attention.
ListShield is aqueous, phage preparation containing six listeria-specific bacteriophages designed to attack a very broad spectrum of "Listeria monocytogenes" strains. 
The Myoviridae is a family of bacteriophages.
It has been divided into four subfamiles and eleven genera.
Many species have not yet been assigned either a genus or a family.
There are at least 130 species in this family. 
There are estimated to be 4,000 bile bears in Vietnam, where their bile can sell for 100,000 dong (~US$6.25) per millilitre (with 37,500 dong a week regarded as the poverty line for an urban resident). 
A teaspoon of seawater contains about one million viruses.
Most of these are bacteriophages, which are harmless to plants and animals, and are in fact essential to the regulation of saltwater and freshwater ecosystems.
They infect and destroy bacteria in aquatic microbial communities, and are the most important mechanism of recycling carbon in the marine environment.
The organic molecules released from the dead bacterial cells stimulate fresh bacterial and algal growth.
Microorganisms constitute more than 90% of the biomass in the sea.
It is estimated that viruses kill approximately 20% of this biomass each day and that there are 15 times as many viruses in the oceans as there are bacteria and archaea.
Viruses are the main agents responsible for the rapid destruction of harmful algal blooms, which often kill other marine life.
The number of viruses in the oceans decreases further offshore and deeper into the water, where there are fewer host organisms.
The effects of marine viruses are far-reaching; by increasing the amount of photosynthesis in the oceans, viruses are indirectly responsible for reducing the amount of carbon dioxide in the atmosphere by approximately 3 gigatonnes of carbon per year.
Like any organism, marine mammals are susceptible to viral infections.
In 1988 and 2002, thousands of harbor seals were killed in Europe by phocine distemper virus.
Many other viruses, including caliciviruses, herpesviruses, adenoviruses and parvoviruses, circulate in marine mammal populations.