The document discusses the synergistic and antagonistic effects of microorganisms interacting in mixed cultures. Synergistic effects occur when microbes work cooperatively to produce an enhanced effect, like the interaction between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in yogurt production. Antagonistic effects happen when microbes inhibit each other through mechanisms like pH changes, toxin production, or competition for resources. These interactions are important in food fermentation processes and can be exploited to obtain desired product characteristics or extend shelf life.

1. Synergistic and
antagonistic
effects of
microorganisms
M. ANZA Adamou

2. Introduction
– The world seen as a system, works following the different interactions between
living beings. Far from the macro aspect of the system, microorganisms also
interact with each other according to their genetic characteristics in order to
ensure their survival as well as their development.
– Most food fermentation processes involve mixed cultures in which different
microbial species interact with each other. These interactions may have neutral,
positive or negative effects on the fitness of the strains performing the
fermentation.(Arioli, Della Scala et al. 2016)

3. Synergistic effect
– Synergy is a type of phenomenon whereby several factors acting together
create an overall effect distinct from anything that could have happened if they
had operated in isolation, either individually or together, but working
independently. There is therefore the idea of creative cooperation.(Wikipédia)
– The synergistic effect of the microorganisms would therefore be the result
obtained by the use of two or more microorganisms functioning in a synergistic
manner in order to obtain a better result.

4. Synergistic effect
– Mixed-strain culture fermentation is an effective approach to
obtain the desired product characteristics and to reduce
fermentation time in most food fermentation processes (Laiño et
al., 2014; Smid and Lacroix, 2013).
– For example, yogurt is typically produced using mixed starter
cultures comprised of Streptococcus thermophilus and
Lactobacillus delbrueckii subsp. bulgaricus.

5. Synergistic effect
– The molecular interactions that play key roles in the mutualistic behaviour of the
yogurt consortium have been investigated using several approaches and have been
reviewed by several authors (Sieuwerts et al., 2008; Smid and Lacroix, 2013).
– Validated interactions between S. thermophilus and L. delbrueckii during the growth
of these species in milk have been described in relation to:
 The availability of nitrogen in milk,
 The exchange of formic acid, pyruvic acid and folic acid,
 The production and utilisation of carbon dioxide,
 And the metabolism of purine, amino acid, long-chain fatty acids and iron.

6. Synergistic effect
– A schematic summary of these metabolic interactions is presented in Fig. 1. As
expected, most of the previously described interactions are trophic interactions
in which the species feed each other with pyruvate, folate, long chain fatty
acids, ornithine, carbon dioxide, peptides, amino acids and putrescine).

7. Fig. 1. Graphic representation of the molecular interactions that play key roles in the mutualistic behaviour of the yogurt consortium. The effect of S. thermophilus urease on urea
hydrolysis and the hypothetical role of the NH3 released by this enzyme on the ...
Stefania Arioli, Giulia Della Scala, Maria Chiara Remagni, Milda Stuknyte, Stefano Colombo, Simone Guglielmetti, Ivano De Noni, Enzio Ragg, Diego Mora
Streptococcus thermophilus urease activity boosts Lactobacillus delbrueckii subsp. bulgaricus homolactic fermentation
International Journal of Food Microbiology, 2016, Available online 20 January 2016
http://dx.doi.org/10.1016/j.ijfoodmicro.2016.01.006

8. Antagonistic effects
– Antagonism is hostility that results in active resistance, opposition, or
contentiousness. It is in this logic that some microorganisms often alter the pH
of the environment (by turning acid), osmotic pressure and surface tension,
with metabolic debris that they secrete. In this case they prevent the activation
or even destroy the enzymes of other microorganisms. Some toxic substances
or antimicrobial products (bacteriocins, antibiotics) also directly control the
replenishment of the other. For example, Lactabacillus strains quickly produce
lactic acid in yoghurt, which prevents other bacteria from reproducing or even
surviving (Canan Öztoprak, 2016).

9. Antagonistic effects
– The antibiotic is used by VVaksmann to explain the effect of antagonist
movement and to produce microorganisms and to inhibit (microbiostatic,
bacteriostatic) and / or lethal (microbiolytic, bacteriolytic) action on other
microorganisms. The penicillins obtained from Penicillium notatum are the first
antibiotic (Aleksandr Fleming). Gramicin synthesized by Bacillus brevis,
Streptomyces fungi synthesized by streptomycin, chloramphenicol,
tetracyclines, kanamycin.

10. Antagonistic effects
– Y. lipolytica contributes to create body and/or texture of the cheese and its
organoleptic characteristics like taste and aroma. Cheese aroma is generated
due to the production of volatile sulfur compounds, including methanethiol,
dimethylsulfide, or dimethyldisulfide.
– Additional benefits include a reduction in ripening times and extended shelf life
of the cheese. Furthermore, Y. lipolytica has anti-listerial activity, and to inhibit
the growth of Bacillus cereus and green mold (Harzevili, 2014).

12. Conclusion
– From all the above, we can retain that microorganisms are living beings that
interact with one another giving rise to various types of biological interaction,
some of which, such as synergy and antagonism, are used in the biological field
and specifically in Food industries. These are two phenomena depending on
their effects are exploited in particular in the production and protection of
foodstuffs.

13. References
– Laiño, J.E., Juarez del Valle, M., Savoy de Giori, G., LeBlanc, J.G., 2014. Applicability of a
Lactobacillus amylovorus strain as co-culture for natural folate bio-enrichment of
fermented milk. Int. J. Food Microbiol. 191, 10–16.
– Smid, E.J., Lacroix, C., 2013. Microbe–microbe interactions in mixed culture food
fermentations. Curr. Opin. Biotechnol. 24, 148–154.
– Arioli, S., et al. (2016). "Streptococcus thermophilus urease activity boosts Lactobacillus
delbrueckii subsp. bulgaricus homolactic fermentation." Int J Food Microbiol.
– Canan Öztoprak, 2016. Mikroorganizmaların beslenmesi ve gelişimi
– Harzevili, F. D. (2014). Biotechnological Applications of the Yeast Yarrowia lipolytica.