{"id":197,"date":"2018-08-21T08:26:27","date_gmt":"2018-08-21T08:26:27","guid":{"rendered":"https:\/\/coliphages.com\/?page_id=197"},"modified":"2024-07-01T11:42:27","modified_gmt":"2024-07-01T11:42:27","slug":"reproduction","status":"publish","type":"page","link":"https:\/\/coliphages.com\/index.php\/reproduction\/","title":{"rendered":"Reproduction"},"content":{"rendered":"

[et_pb_section fb_built=”1″ _builder_version=”4.16″ global_colors_info=”{}”][et_pb_row module_class=” et_pb_row_fullwidth” _builder_version=”4.16″ width=”89%” width_tablet=”80%” width_last_edited=”on|desktop” max_width=”89%” max_width_tablet=”80%” max_width_last_edited=”on|desktop” custom_padding=”2px|0px|25.85px|0px|false|false” make_fullwidth=”on” locked=”off” global_colors_info=”{}” column_structure=”2_3,1_3″ width_phone=”80%” max_width_phone=”80%”][et_pb_column type=”2_3″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_text _builder_version=”4.16″ text_font=”|700|||||||” text_text_color=”#256168″ text_font_size=”44px” text_line_height=”1.1em” header_font=”||||||||” header_line_height=”1.7em” text_font_size_tablet=”” text_font_size_phone=”33px” text_font_size_last_edited=”on|phone” global_colors_info=”{}”]How do bacteriophages reproduce?
\n[\/et_pb_text][et_pb_text _builder_version=”4.16″ text_font=”||||||||” text_text_color=”#256168″ text_font_size=”25px” text_line_height=”1.1em” background_color=”#eaeddb” custom_margin=”|||” custom_padding=”60px||60px|95px|true” custom_padding_tablet=”” custom_padding_phone=”40px|20px|40px|30px|true” custom_padding_last_edited=”on|phone” text_font_size_tablet=”” text_font_size_phone=”20px” text_font_size_last_edited=”on|phone” locked=”off” global_colors_info=”{}”]2.1<\/strong> Lytic cycle<\/a>
\n2.2<\/strong> Lysogenic cycle<\/a>
\n[\/et_pb_text][et_pb_text _builder_version=”4.16″ text_font=”||||||||” text_line_height=”1.3em” header_font=”||||||||” header_2_font=”|700|||||||” header_2_text_color=”#0a2d31″ header_2_font_size=”33px” text_font_size_tablet=”” text_font_size_phone=”18px” text_font_size_last_edited=”on|phone” global_colors_info=”{}”]<\/p>\n

Bacteriophages<\/strong> are non-cellular<\/strong> and non-metabolic<\/strong> living organisms. This means that they are forced parasites<\/strong> and thus they can only replicate inside a bacterial cell<\/strong>, usually called a host cell (host bacteria).<\/p>\n

Bacterial cell-supporting phage replication needs<\/strong> to meet two fundamental requirements: it has to be a living cell<\/strong>, and it has to be metabolically active<\/strong>.<\/p>\n

Bacteriophages follow two strategies for reproducing: the lytic cycle<\/strong> and the lysogenic cycle. The one that matters for the purpose of using phages as indicators<\/strong> is the lytic one, as no free virions are produced in the lysogenic cycle. (Adams, 1959, Bott, 2014)<\/p>\n

[\/et_pb_text][\/et_pb_column][et_pb_column type=”1_3″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_image src=”https:\/\/coliphages.com\/wp-content\/uploads\/2018\/09\/cta-bluephage.jpg” url=”http:\/\/bluephage.com\/” url_new_window=”on” align_tablet=”center” align_last_edited=”on|desktop” _builder_version=”4.16″ global_colors_info=”{}” align_phone=”center”][\/et_pb_image][\/et_pb_column][\/et_pb_row][et_pb_row module_class=” et_pb_row_fullwidth” _builder_version=”4.16″ width=”89%” width_tablet=”80%” width_last_edited=”on|desktop” max_width=”89%” max_width_tablet=”80%” max_width_last_edited=”on|desktop” make_fullwidth=”on” global_colors_info=”{}” width_phone=”80%” max_width_phone=”80%”][et_pb_column type=”4_4″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_text _builder_version=”4.25.2″ text_font=”||||||||” text_line_height=”1.3em” header_font=”||||||||” header_2_font=”|700|||||||” header_2_text_color=”#0a2d31″ header_2_font_size=”33px” hover_enabled=”0″ text_font_size_tablet=”” text_font_size_phone=”18px” text_font_size_last_edited=”on|phone” global_colors_info=”{}” module_id=”2-1″ sticky_enabled=”0″]<\/p>\n

2.1 Lytic cycle<\/h2>\n

The process of the lytic cycle<\/strong> is divided into five steps.<\/p>\n

First of all, the virus has to find and attach<\/strong> to the surface of the target bacteria. This attachment<\/strong> depends on the presence of specific receptors on the cell surface<\/strong> and determines the specificity and host range<\/strong> of a given bacteriophage. Different bacteriophages have different strategies or target molecules.<\/p>\n

Most bacteriophages use cell wall molecules as receptors<\/strong>. These are known as somatic bacteriophages<\/strong>. Myoviridae<\/em>, Siphoviridae<\/em>, Podoviridae<\/em> and Microviridae<\/em> belong to this group. Another strategy is to use cell appendixes like F pili or flagella. These are called F-specific bacteriophages<\/strong>, which use the F or sexual pili as receptors and as a channel for \u201cinjecting\u201d their nucleic acid<\/strong>. The Inoviridae<\/em> and Leviviridae<\/em> belong to this group.<\/p>\n

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There is no active positive attraction (positive taxis) between phages and host bacteria and consequently meeting of bacteria and phages depends on random encounters<\/strong>. Whether these encounters occur or not depends<\/strong> to a great extent on the concentrations of bacteria and bacteriophages<\/strong>. Some studies performed with somatic coliphages indicate that the sum of log10<\/sub><\/strong> concentrations of phages and host bacteria per ml that guarantee replication is around 6.5<\/strong> (Jofre, 2009).<\/p>\n

The second step is penetration<\/strong>, which consists of the injection of the viral genome and seldom molecules<\/strong> contained inside the capsid into the bacterial cytoplasm. This can happen through the cell wall (somatic bacteriophages) or through an appendage (flagella and the sexual pili).<\/p>\n

Then the viral genome, using the metabolic tools of the host cell<\/strong>, starts replicating<\/strong> and the production of viral proteins takes place. This step requires the host to be metabolically active<\/p>\n

When feces exit the gut, the change of environment causes a stress<\/strong> on the great majority of fecal bacteria, including coliform bacteria, that leads<\/strong> first to metabolic inactivity and<\/strong> then to death<\/strong>. This, together with the difficulties for viruses to come across a cell in a liquid matrix with a relatively poor concentration of phages and bacteria, makes viral reproduction outside the gut barely possible<\/strong> (Jofre, 2009).<\/p>\n

The fourth step is the assembly of<\/strong> the different proteins and the genome, forming the capsomers<\/strong> that bind<\/strong> with each other<\/strong> and with the genetic material<\/strong> to build the capsid<\/strong>, and hence producing newborn virions<\/strong> which become visible (by electron microscopy) inside the bacterial cytoplasm.<\/p>\n

Finally, the bacterial cell breaks<\/strong>, in a process known as lysis<\/strong>, due to enzymatic action of some proteins coded in the viral genome, and new bacteriophages<\/strong> are released<\/strong> to the media. Some bacteriophages, such as for example M13, do not lyse the cell, but this seems to be exceptional.<\/p>\n

All this process can happen in less than 30 minutes, and at the end between 100<\/strong> and 200<\/strong> (depending on the bacteriophage) new infectious phage particles are released<\/strong>.<\/p>\n

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The amount of phages formed inside a host<\/strong> bacterium and released by cell lysis is known as the burst size<\/strong>.<\/p>\n

[\/et_pb_text][et_pb_text _builder_version=”4.25.2″ text_font=”||||||||” text_line_height=”1.3em” header_font=”||||||||” header_2_font=”|700|||||||” header_2_text_color=”#0a2d31″ header_2_font_size=”33px” hover_enabled=”0″ text_font_size_tablet=”” text_font_size_phone=”18px” text_font_size_last_edited=”on|phone” global_colors_info=”{}” sticky_enabled=”0″]<\/p>\n

During steps 2 and 3 the infectious and visible virions disappear.<\/p>\n

[\/et_pb_text][et_pb_text _builder_version=”4.25.2″ text_font=”||||||||” text_line_height=”1.3em” header_font=”||||||||” header_2_font=”|700|||||||” header_2_text_color=”#0a2d31″ header_2_font_size=”33px” hover_enabled=”0″ text_font_size_tablet=”” text_font_size_phone=”18px” text_font_size_last_edited=”on|phone” global_colors_info=”{}” module_id=”2-2″ sticky_enabled=”0″]<\/p>\n

2.2 Lysogenic cycle<\/h2>\n

This cycle follows the same start as<\/strong> the lytic<\/strong> one, but once the viral genome<\/strong> penetrates, it integrates within<\/strong> the bacterial DNA<\/strong> or in some cases remains as a plasmic. When integrated, it replicates at the same time as the bacterial one. It can replicate at its own rate if it forms a plasmid, but no virions are produced unless it passes to a lytic cycle due to lysogenic induction<\/strong>, usually as a consequence of a stress situation<\/strong>. This cycle is important for bacterial genetic variability<\/strong> but not for detecting fecal contamination, as we cannot quantify the virus that are in a lysogenic cycle.<\/p>\n

[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row module_class=” et_pb_row_fullwidth” _builder_version=”4.16″ width=”89%” width_tablet=”80%” width_last_edited=”on|desktop” max_width=”89%” max_width_tablet=”80%” max_width_last_edited=”on|desktop” custom_padding=”31.7833px|0px|0|0px|false|false” make_fullwidth=”on” global_colors_info=”{}” width_phone=”80%” max_width_phone=”80%”][et_pb_column type=”4_4″ _builder_version=”4.16″ custom_padding=”|||” global_colors_info=”{}” custom_padding__hover=”|||”][et_pb_divider divider_weight=”2px” _builder_version=”4.16″ max_width=”20%” global_colors_info=”{}”][\/et_pb_divider][et_pb_text _builder_version=”4.16″ text_font=”|700|||||||” text_text_color=”#256168″ text_font_size=”33px” global_colors_info=”{}”]<\/p>\n

References<\/p>\n

[\/et_pb_text][et_pb_text _builder_version=”4.16″ text_font=”||||||||” text_font_size=”15px” text_line_height=”1.3em” background_color=”#eaeddb” custom_padding=”50px|50px|50px|50px|true|true” custom_padding_tablet=”” custom_padding_phone=”40px|30px|40px|30px|true|true” custom_padding_last_edited=”on|phone” text_font_size_tablet=”” text_font_size_phone=”12px” text_font_size_last_edited=”on|phone” global_colors_info=”{}”]<\/p>\n

Adams, M.H. (1959).<\/em> Bacteriophages<\/strong>. Interscience Publishers. Inc. New York.<\/p>\n

Bott, R. (2014).<\/em> Brock Biology of Microorganisms<\/strong>, 14th Edition, Madigan, M.T. Igarss 2014.<\/p>\n

Jofre, J. (2009).<\/em> Is the replication of somatic coliphages in water environments significant?<\/strong> J. Appl. Microbiol 106 : 1059-1069.<\/p>\n

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How do bacteriophages reproduce? 2.1 Lytic cycle 2.2 Lysogenic cycle Bacteriophages are non-cellular and non-metabolic living organisms. This means that they are forced parasites and thus they can only replicate inside a bacterial cell, usually called a host cell (host bacteria). Bacterial cell-supporting phage replication needs to meet two fundamental requirements: it has to be […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_et_pb_use_builder":"on","_et_pb_old_content":"","_et_gb_content_width":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-197","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/pages\/197","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/comments?post=197"}],"version-history":[{"count":35,"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/pages\/197\/revisions"}],"predecessor-version":[{"id":966,"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/pages\/197\/revisions\/966"}],"wp:attachment":[{"href":"https:\/\/coliphages.com\/index.php\/wp-json\/wp\/v2\/media?parent=197"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}