killing bacteria with lemon and garlic

[jackrob15]

I am doing a science experiment write up and lemon in my experiement 'killed' bacteria on a agar plate along with garlic. Do these have antibacteria properties and why. What in them does it, and is lemon just purely acting as an acid which kills bacteria???

Thanx

[caddis]

garlic contains allicin, which is a natural antiseptic. it is released when the clove is crushed or chopped. beneficial when eaten raw but not cooked
http://www.garlic-central.com/allicin.html
as for lemon it is more likely the essential oil rather than the citric acid itself

[theprof]

Garlic has both bacteriostatic and bactericidal properties.

Garlic contains many complex sulphur-containing compounds. One of these is a substance called alliin. When garlic is damaged by cutting,crushing etc, the alliin reacts with an enzyme called allinase. The allinase then chemically changes the alliin to allicin.

Allicin is the "magical" ingredient of garlic. It interferes with lipid synthesis at cellular level as well as hindering production of RNA.

Without correct lipid synthesis, the phospholipid layer of a cell wall cannot develop correctly in most bacteria and the bacteria die soon after fission.

Without RNA, cells find it almost impossible to synthesize proteins although this can also occur with diminished RNA production.
The reason this happens is that every stage of RNA production would be stopped by the absence of messenger RNA, ribosomal RNA and transfer RNA.
You are probably aware that if proteins and their constituent amino acids cannot be produced, then an organism cannot develop and grow as they are vital for every part of a cell.

There have been some papers published in recent years discussing the effect of garlic on viruses. It is known that raw garlic destroys viral origin pneumonia, herpes, cytomegalovirus, vaccinia and meningitis infections both in vivo and in vitro. Many other viruses are also susceptible.

As a result of these many methods of hindering growth, Allicin may be regarded as a very effective bacterial and viral "antiseptic"

(continued)

[theprof]

(Continued)

There have been some fears in recent years that bacteria and viruses will eventually become immune to Garlic.

I doubt this will ever happen as the allicin reacts with the sulphahydryl groups within enzymes in a manner which prevents the enzymes from performing their function.

For these enzymes to develop immunity to garlic, it would mean their DNA would have to be modified to prevent the SH groups being affected. This is unlikely to happen as they would then cease to function as enzymes

Finally, despite all my knowledge gained on this matter from years as a biochemist, I can tell you I can�t stand the taste or smell of the stuff!

[theprof]

With regard to lemon, the bactericidal and antiseptic properties are due mainly to the essential oils that lemon contains.
Streptococcus, Staphylococcus and others are susceptible to its effects within hours of exposure.
Lemon oil also has weak anti-fungal and anti-viral properties.

[jackrob15]

Wow. Great information and I understood it all. Your help is very much appreciated. Thanks.

[theprof]

No problem - don't hesitate to ask if you need further help.

Thanks for the thanks!