Lactobacilli on Plants

Abstract

The distribution, enumeration, and identification of lactobacilli on vegetable plants were studied in an area described geographically as being subtropical and moist. The lactobacilli were obtained, by means of quantitative enrichment procedures in Rogosa's SL broth, from 35.3% of all samples incubated at 32 C, and from 15.4%, of the samples incubated at 45 C. Less than 10 lactobacilli/g of plant material were enumerated in 54% of all positive samples. The lactobacilli were found much less frequently and in lower numbers than were streptococci or Leuconostoc mesenteroides. The most frequently isolated lactobacillus was very simular to, but not identical with, Lactobacillus fermenti. It was aerogenic, grew well at both 15 and 45 C, fermented arabinose, lactose, and sucrose, and liberated ammonia from arginine. Of the identified species, L. plantarum, L. fermenti, and L. brevis were the most frequently isolated, whereas L. casei, L. viridescens, L. cellobiosus, L. salivarius, and L. buchneri were obtained from small numbers of samples. The widespread but sporadic distribution of lactobacilli in low numbers seems to indicate that these organisms do not normally thrive on plant surfaces. A ternary cycle, beginning with intestinal waste, followed by mechanical distribution to and among plants, and return to the host via the oral cavity, is suggested.

Microbial ecology of fermenting plant materials

“…Plants harbor a numerous and varied microflora. Although the numbers of lactic acid bacteria on plant materials are highly variable, most investigations have shown that their number is very low, often in the range of 10-1000 cells per g [12][13][14][15][16][17], which represents approx. 0.01-1.0% of the total microbial population.…”

“…Besides the increase in total number, the distribution among different types of microorganisms changes. The dominating, aerobic, Gram-negative bacteria are replaced by facultative and anaerobic, Gram-positive bacteria of the genera Leuconostoc, Lactobacillus, Pediococcus, Bacillus, and Clostridiurn [15][16][17]21,22]. However, in lactic acid fermentation of plants like alfalfa, ryegrass, cucumbers, carrots, and red beets, it has been shown that Gram-negative bacteria of the family Enterobacteriaceae can be present in high numbers and cause problems such as excessive gas in cucumbers [23] and pectinolytic softening in carrots and beets [12].…”

“…Growth of the heterofer-361 menter, L. mesenteroides, is undesirable from a product viewpoint since the CO z produced contributes [30,31] to gaseous spoilage. Although L. mesenteroides is not as acid-tolerant as the other species, it generally initiates the fermentation because it is present at an initially higher number than the other lactic acid bacteria associated with the fresh cucumbers [16].…”

Characterization and Distribution of Lactobacilli during Lactic Fermentation of Okra (Hibiscus esculentus)

“…2). Mundt and Hammer (1968) reported that they isolated the following lactobacilli from okra plants: L. plantarum, L. fermenti and L. casei. The species of the genus Lactobacillus that were isolated from okra fruits were not identical to the identified strains of okra plants.…”

“…Lactobacillus brevis and Lactobacillus plantarum are responsible for the natural fermentation of many vegetables, although L. plantarum is by far the predominant species in most fermentations (Etchells et al, 1975). Mundt and Hammer (1968) studied the distribution of lactobacilli on okra plants. No attempt to study the microflora during fermentation of okra fruits is reported.…”