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Cell growth can also be influenced by the presence of other microorganisms, such as lactic acid bacteria, ''Saccharomyces'' and ''Brettanomyces''. One study by Hübbe showed that ''L. brevis'' and ''L. parabrevis'' grew to the normal high cell counts when grown individually and without competition. When co-fermented with ''Brettanomyces'', the cell count of ''L. brevis'' was halved, and the growth rate of ''L. parabrevis'' was greatly diminished to about 15-20%, indicating that the ability of ''Lactobacillus'' to compete with ''Brettanomyces'' is species dependent. The pitching rate of ''Brettanomyces'' was also tested, and seemed to not have an effect on the ''Lactobacillus'' growth. When co-fermented with both ''S. cerevisiae'' and ''Brettanomyces'', the ''Lactobacillus'' growth was greatly diminished to about 2-13% of what the normal cell growth was without competition. This appears to correspond with anecdotal reports from brewers that some ''Lactobacillus'' species/strains do not compete well with yeast, especially ''S. cerevisiae''. The growth of ''Brettanomyces'', however, was not affected by the presence of ''Lactobacillus'' <ref name="Hubbe">[https://www.facebook.com/groups/MilkTheFunk/permalink/1407620509266159/ Effect of mixed cultures on microbiological development in Berliner Weisse (master thesis). Thomas Hübbe. 2016.]</ref>.
Brian Martyniak showed that ''Brettanomyces'' growth can be inhibited by the concurrent growth of ''S. cerevisiae'' under anaerobic conditions. In aerobic conditions, oxygen appears to help ''Brettanomyces'' out-compete ''S. cerevisiae''when ''S. cerevisiae'' is present in small quantities. The presence of lactic acid bacteria does not greatly effect ''Brettanomyces'' growth <ref name="Hubbe" /><ref name="martyniak">[https://www.facebook.com/groups/MilkTheFunk/permalink/1362220513806159/ MTF post by Brian Martyniak on ''Brettanomyces'' growth in competition with ''Saccharomyces'' under aerobic and anaerobic conditions. 07/29/2016.]</ref>. Hübbe showed a similar result by showing that both ''B. bruxellensis'' and ''B. anomalus'' grew essentially the same amount by themselves or with ''Lactobacillus'', but growth for both ''Brettanomyces'' species was greatly inhibited when co-fermented with ''S. cerevisiae''. Therefore, when making starters for mixed cultures of ''Brettanomyces'' and ''Saccharomyces'', the brewer might be able to favor ''Saccharomyces'' by limiting oxygen, or favor ''Brettanomyces'' by introducing oxygen during growth. Data from Thomas Hübbe and Mark Trent support that the initial pitching rate doesn't have a great effect on the final cell count in pure ''Brettanomyces'' starters or beer, indicating that ''Brettanomyces'' is fairly forgiving in regards to small initial cell counts <ref name="Hubbe" /><ref>[[Brettanomyces_Propagation_Experiment|MTF ''Brettanomyces'' Propagation Experiment]]</ref>.
* See also [[Mixed Fermentation]].