Secundilactobacillus (Se.cun.di.lac.to.ba.cil’lus. L. adj. secundus, second or next, following; N.L. masc. n. Lactobacillus a bacterial genus name; N.L. masc. n. Secundilactobacillus a lactobacillus that occurs in a secondary fermentation or as a spoilage organism after primary fermenters depleted hexoses and disaccharides).

Gram-positive, rod-shaped, catalase negative, heterofermentative. Most strains grow at 15 °C and some also grow at 45 °C, the pH range of growth is highly variable. The genome size ranges from 1.85 Mbp for S. oryzae to 3.62 Mbp for S. collinoides, the mol% G+C content of DNA ranges from 41.03–47 %. Strains in the genus lead a free-living lifestyle and were isolated as secondary fermentation or spoilage organisms from hexose-depleted habitats including silage, beer, liquor mashes and apple cider. Metabolic properties of Secundilactobacillus species match adaptation to hexose-depleted habitats. Many strains of the genus do not reduce fructose to mannitol, a trait which differentiates Secundilactobacillus from all other heterofermentative lactobacilli except Paucilactobacillus. Many strains in the genus metabolize diols via diol-hydratase and convert agmatine, a metabolite of arginine decarboxylation, via the agmatine deiminase pathway. Strains in the genus generally harbour genes coding for transaldolase/transketolase which mediate metabolism of pentoses to pyruvate.

A phylogenetic tree on the basis of 16S rRNA genes of all species in the genus Secundilactobacillus is provided in Fig. S6O.

The type species of the genus is Secundilactobacillus malefermentans comb. nov.; Secundilactobacillus was previously referred to as the Lactobacillus collinoides group.