Abstract
Lactobacilli are Gram-positive aerotolerant organisms that comprise the largest genus of Lactic Acid Bacteria (LAB). Most lactobacilli are devoid of the antioxidant enzymes, superoxide dismutases, and catalases, required for protection against superoxide radicals and hydrogen peroxide (H2O2), respectively. However, some lactobacilli can accumulate millimolar concentrations of intracellular manganese and spare the need for superoxide dismutase, while others possess non-heme catalases. L. plantarum is associated with plant materials and plays an important role in fermented foods and gut microbiomes. Therefore, understanding the effects of the environment on the growth and survival of this organism is essential for its success in relevant industrial applications. In this report, we investigated the physiological role of Mn-catalase (MnKat) in Lactobacillus plantarum ATCC 14431. To this end, we compared the physiological and morphological properties of a ΔMnkat mutant strain and its isogenic parental strain L. plantarum ATCC 14431. Our data showed that the MnKat is critical for the growth of L. plantarum ATCC 14431 in the presence of oxygen and resistance to H2O2. The aerobic growth of the mutant in presence or absence of H2O2 was improved in the Mn-rich medium (APT) as compared to the growth in MRS medium. Furthermore, under aerobic conditions the mutant strain possessed atypical cellular morphology (i.e., shorter, and fatter). In conclusion, the MnKat of L. plantarum ATCC 14431 is important for aerobic growth, protection against H2O2, and maintenance of the rod-shaped cell morphology under aerobic conditions.
Highlights
Lactic acid bacteria (LAB) include a diverse group of microaerophilic, Gram-positive organisms that are generally regarded as catalase negative
Lactobacilli comprise the largest genus of the LAB group and occupy habitats ranging from foodstuffs to the microbiomes of humans and animals
Lactic acid bacteria (LAB) are generally classified as catalase negative and incapable of synthesizing heme; heme-dependent catalases have been reported in some lactobacilli when an external source of heme is provided (23)
Summary
Lactic acid bacteria (LAB) include a diverse group of microaerophilic, Gram-positive organisms that are generally regarded as catalase negative. Lactobacilli comprise the largest genus of the LAB group and occupy habitats ranging from foodstuffs to the microbiomes of humans and animals. In the presence of oxygen, lactobacilli generate reactive oxygen species (ROS) (i.e., superoxide radicals (O2 − ), hydrogen peroxide (H2 O2 ), and hydroxyl radicals (HO)). In presence of oxygen, they can accumulate up to millimolar concentrations of H2 O2 [1,2,3,4,5,6]. Mechanisms to combat the toxicity of ROS in LAB are essential for their aerobic survival. Understanding the mechanisms for combating oxidative stress in these economically important organisms is a critical element in maximizing their role in fermented foods, as well as in human and animal microbiome/health
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