RESUMEN
High levels of gums such as dextran, produced by Leuconostoc and Lactobacillus spp., have a severe impact on factory throughput and sugar quality. This study aimed to determine the phylogenetic relationships between gum-producing Leuconostoc and Lactobacillus bacteria which were isolated from various locations in a sugarcane processing factory at times when low- and high-dextran raw sugar, respectively, were produced. Phylogenetic analysis of 16S rRNA gene sequences grouped 81 isolates with the type strains of Leuconostoc mesenteroides (subspp. mesenteroides, dextranicum, and cremoris), Leuconostoc pseudomesenteroides, Leuconostoc lactis, and Leuconostoc citreum, respectively. Forty-three isolates clustered with the type strain of Lactobacillus fermentum. The phylogenetic relatedness of the isolates was determined by sequencing and analysis of the housekeeping genes rpoA and dnaA for Leuconostoc spp. and the pheS and tuf genes for the Lactobacillus spp. The rpoA gene proved discriminatory for the phylogenetic resolution of all of the isolated Leuconostoc spp. and the dnaA housekeeping gene was shown to be effective for isolates clustering with the type strains of Leuc. mesenteroides and Leuc. citreum. None of the loci examined permitted differentiation at the subspecies level of Leuc. mesenteroides. Single-locus analysis, as well as the concatenation of the pheS and tuf housekeeping gene sequences, yielded identical phylogenies for the Lactobacillus isolates corresponding to L. fermentum.
Asunto(s)
Dextranos/metabolismo , Genes Esenciales/genética , Lactobacillus/clasificación , Leuconostoc/clasificación , Saccharum/microbiología , Proteínas Bacterianas/genética , ADN Bacteriano/genética , Proteínas de Unión al ADN/genética , ARN Polimerasas Dirigidas por ADN/genética , Amplificación de Genes , Lactobacillus/genética , Lactobacillus/aislamiento & purificación , Leuconostoc/genética , Leuconostoc/aislamiento & purificación , Filogenia , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADNRESUMEN
A previous study reported on the isolation of 430 polysaccharide (gum)-producing bacteria from a South African sugarcane processing factory and the identification of isolates by comparative 16S rRNA gene sequencing. A large number of isolates (202) belonged to the genus Weissella and clustered with reference strains of Weissella cibaria and Weissella confusa. In this study, we identified 147 strains as W. cibaria and 55 as W. confusa based on phylogenetic analyses of pheS and dnaA gene sequences of representative isolates. We also included atpA gene sequence analysis of Weissella isolates as potential future phylogenetic marker to differentiate amongst strains of W. cibaria and W. confusa.
Asunto(s)
Genes Bacterianos/genética , Filogenia , Saccharum/microbiología , Weissella/clasificación , Weissella/genética , Microbiología de Alimentos , ARN Ribosómico 16S/genética , Análisis de Secuencia de ADN , Sudáfrica , Weissella/aislamiento & purificaciónRESUMEN
Polysaccharide (gum)-producing bacteria are responsible for severe economic losses in the sugarcane processing industry. Increased polysaccharide levels in raw sugar are normally an indication that biodeterioration occurred in the cane, soon after harvesting. Once in the sugar processing plant, the cell numbers of gum-producing bacteria escalate and may reach levels difficult to control. We have isolated 430 gum-producing bacteria from sugarcane and different sampling points in a South African sugarcane processing factory. As expected, high cell numbers of gum-producing bacteria were isolated from the factory during a time when sugar with a high dextran content was produced. What we did not expect was to find the same species in the factory at a time when sugar with a low dextran content was produced. Phylogenetic analyses of the 16S rRNA gene sequences differentiated the gum-producing bacteria into four genera and nine species. The majority of these isolates belonged to the genus Weissella (47%), followed by members of Bacillus (24%), Leuconostoc (19%) and Lactobacillus (10%). For the first time, we report on the isolation of Weissella confusa, Weissella cibaria and Bacillus amyloliquefaciens from a sugarcane processing factory.