Pozol is a beverage prepared with maize dough made after boiling the kernels in limewater. This pretreatment could act as a selective force that shapes the starter microbiota, with microorganisms able to survive the fermentation. Since Streptococcus infantarius subsp. infantarius (Sii) dominates in pozol, we evaluated the effect of acid and alkali stresses on strain Sii-25124 in commercial APT broth as a first attempt to assess its adaptation capacity. Results suggest that Sii-25124 has adaptative advantages to pH changes that possibly contribute to its persistence even after the acidification of the dough. Its cardinal pH values were 4.0 and 11.0, with an optimum between 6.6 and 8.0. It showed alkali tolerance unlike other pozol Sii strains. Adaptation at pH 4.0, 10.0 and 11.0, compared with non-adapted cells, induced acid tolerance enhancing survival at pH 3.6 (P < 0.05); a 2 min heat shock at 62 °C induced alkali tolerance response enhancing survival at pH 10.5 (P < 0.05). The up-regulation of dnaK, groEL, ptsG and atpB was observed during 5 h of exposition at pH 3.6, 4.0 and 10.0, showing similar expression rates after induction by acid shock or alkaline stress. Changes of atpB were more evident having almost five-fold induction during long-term stress.

中文翻译：

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婴儿链球菌亚种对酸和碱的耐受性。从发酵的尼克斯塔姆面团中分离的婴儿菌种25124：Pozol。在APT肉汤中研究。

Pozol是一种将玉米粒在石灰水中煮沸后制成的玉米面团制成的饮料。这种预处理可以作为一种选择力，使发酵菌形成微生物，使微生物能够在发酵过程中存活下来。由于婴儿链球菌亚种。婴儿（Sii）在pozol中占主导地位，我们评估了酸和碱胁迫对商业APT肉汤中Sii-25124菌株的影响，这是评估其适应能力的首次尝试。结果表明，即使面团酸化后，Sii-25124仍具有适应pH值变化的适应性优势，这可能有助于其持久性。其主要pH值为4.0和11.0，最佳为6.6和8.0。与其他pozol Sii菌株不同，它具有耐碱性。与非适应性细胞相比，在pH 4.0、10.0和11.0下的适应性，诱导的耐酸性提高了在pH 3.6下的存活率（P <0.05）在62°C下2分钟的热激诱导了碱耐受性响应，从而提高了pH 10.5下的存活率（P <0.05）。在pH值为3.6、4.0和10.0的情况下，在暴露的5小时内观察到了dnaK，groEL，ptsG和atpB的上调，在酸冲击或碱性胁迫诱导后显示出相似的表达率。在长期压力下，atpB的变化更为明显，具有近五倍的诱导作用。