The purpose of this review article on the lactic acid bacteria grew from an early curiosity and a desire to convey and impart the broad scope of literary information on their functions as starter cultures, in the manufacture of fermentation products such as dairy products and alcoholic beverages, as well as their contribution to better health. This review article is an attempt to empower the reader and to circumvent the difficult task in acquiring and elucidating a large body of information. The intent is to familiarize the reader with the various lactic species, their habitat or source, associated food, physiological characteristics, colonial morphology, biochemical characteristics, culture media (enrichment, nonselective, and selective), classic description, and taxonomy. This review provides information on Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Carnobacterium, and Enterococcus. Trends are presented, such as the use of nisin to extend food shelf-life and the current research premise that Probiotic strains may alter the intestinal flora and thus prevent intestinal wall penetration by pathogens.

The Lactic Acid Bacteria: A Literature Survey

Transfer of Streptococcus lactis and Related Streptococci to the Genus Lactococcus gen. nov.

Several starch-hydrolyzing strains of Lactobacillus Beijerinck 1901 were isolated from cattle waste-corn fermentations. The isolates were facultatively anaerobic, gram-positive, nonmotile, nonsporeforming, rod-shaped organisms that grew singly and in short chains, produced lactic acid and small amounts of acetic acid but no gas from glucose, and did not exhibit oxidase-, catalase-, or nitrate-reducing activities. Growth occurred at 45°C but not at 15°C. dl-Lactic acid was synthesized from glucose. An extracellular amylolytic enzyme was formed. The organisms fermented amygdalin, cellobiose, esculin, fructose, galactose, glucose, maltose, mannose, salicin, starch, sucrose, and trehalose. Some strains fermented mannitol and lactose. Arabinose, gluconate, melezitose, melibiose, raffinose, rham-nose, ribose, and xylose were not fermented. The average guanine-plus-cytosine content of the deoxyribonucleic acid was 40.4 mol%. Reassociation values of 15% or less were obtained with the deoxyribonucleic acids of the starch hydrolyzers and those of the type strains of Lactobacillus acidophilus (Moro) Hansen and Mocquot 1970; Lactobacillus jensenii Gasser, Mandel, and Rogosa 1970; and Lactobacillus leichmanii (Henneberg) Bergey et al. 1923. The new species was differentiated from the three recognized species on the basis of starch fermentation, vitamin requirements, guanine-plus-cytosine contents, and stereoisomerism of lactic acid produced. It was concluded that these organisms represent strains of a hitherto unrecognized species for which the name Lactobacillus amylovorus is proposed. The type strain of L. amylovorus is NRRL B-4540.

Lactobacillus amylovorus, a New Starch-Hydrolyzing Species from Cattle Waste-Corn Fermentations

Lactococcus lactis is one of the most important micro-organisms in the dairy industry for the fermentation of cheese and buttermilk. Besides the conversion of lactose to lactate it is responsible for product properties such as flavor and texture, which are determined by volatile metabolites, proteolytic activity and exopolysaccharide production. While the species Lactococcus lactis consists of the two subspecies lactis and cremoris their taxonomic position is confused by a group of strains that, despite of a cremoris genotype, display a lactis phenotype. Here we compared and analyzed the (draft) genomes of 43 L. lactis strains, of which 19 are of dairy and 24 are of non-dairy origin. Machine-learning algorithms facilitated the identification of orthologous groups of protein sequences (OGs) that are predictors for either the taxonomic position or the source of isolation. This allowed the unambiguous categorization of the genotype/phenotype disparity of ssp. lactis and ssp. cremoris strains. A detailed analysis of phenotypic properties including plasmid-encoded genes indicates evolutionary changes during niche adaptations. The results are consistent with the hypothesis that dairy isolates evolved from plant isolates. The analysis further suggests that genomes of cremoris phenotype strains are so eroded that they are restricted to a dairy environment. Overall the genome comparison of a diverse set of strains allowed the identification of niche and subspecies specific genes. This explains evolutionary relationships and will aid the identification and selection of industrial starter cultures.

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Comparative Genome Analysis of Lactococcus lactis Indicates Niche Adaptation and Resolves Genotype/Phenotype Disparity.

The bacterium that causes Pierce's disease of grapevines is isolated most consistently from the foregut of its leafhopper vector Graphocephala atropunctata. As seen in light and scanning electron microscopy of infective leafhoppers, the bacteria are attached to the cibarial pump and the lining of the esophagus in the foregut where they appear to multiply. These findings suggest that the bacterium is transmitted from the foregut by egestion during feeding by infective leafloppers .

https://science.sciencemag.org/content/sci/206/4420/839.full.pdf

Pierce's Disease Bacterium: Mechanism of Transmission by Leafhopper Vectors.

A gram-positive, rod-shaped bacterium, originally thought by Auger (1974) to be the agent of Pierce's disease of grapevines, is commonly associated with Hordnia circellata, one of the leafhopper vectors of the disease. The bacterium has the following colonial and cellular characteristics: smooth, glistening white, or chalky colonies, 0.4 to 0.5 mm in diameter with entire margins; gram positive becoming gram variable after 5 days in culture; nonmotile and nonsporeforming; grows between 15 and 37°C with an optimum between 28 and 30°C and no growth at 9 or 45°C; optimum growth occurs at pH 6.5, with growth observed at pH 4.5 and pH 9.0. The bacterium does not survive after 5 to 7 days of growth and must be maintained on fresh medium. It is rod-shaped (0.6 by 1.5 to 2.0 μm), growing in short chains of three to four cells each, and possesses mesosomes and a cell wall of uniform thickness (28 to 35 nm) that consists of an electrondense outer layer and an inner layer resembling unit-membrane structure. The organism is a facultative anaerobe which reacts negatively in tests for cytochrome oxidase, catalase, “gelatinase,” urease, tryptophanase, and nitrate and disulfide reductase activities. No dextran or levan is produced from sucrose. It produces L-(+)-lactic acid but not D-(—)-lactic acid from glucose and sucrose fermentation, acetylmethylcarbinol, or arginine deaminase. Glucose, sucrose, galactose, maltose, fructose, trehalose, salicin, inulin, and cellobiose, but not gluconate, lactose, mannose, mannitol, sorbitol, melibiose, or raffinose, were utilized as carbon sources. Its chromosome has an average guanine-plus-cytosine content of 32.75 mol%. Based on these features, the bacterium appears to be a hitherto unrecognized species of the genus Lactobacillus, for which the name Lactobacillus hordniae sp. nov. is proposed. The type strain is HC-1 (= ATCC 29071).

C. I. Kado

Papers

Lactobacillus hordniae, a New Species from the Leafhopper (Hordnia circellata)