SDS-PAGE Of Whole-cell Proteins Research Articles

Technological properties and bacteriocins production by Lactobacillus curvatus 54M16 and its use as starter culture for fermented sausage manufacture

Lactobacillus curvatus 54M16 was isolated from traditional fermented sausages of Campania region (Italy) and identified by 16S rRNA and hsp60 gene sequencing and by SDS-PAGE of whole cell proteins. The strain produced more than one bacteriocin, carrying the genes for sakacin X, T and P as demonstrated by PCR studies. The ability of L. curvatus 54M16 to produce multiple bacteriocins is confirmed by molecular mass spectrometry analysis and N-terminal amino acid sequencing. Among the bacteria tested, the pathogens Listeria monocytogenes and Bacillus cereus and the meat spoilage Brochotrix thermosphacta were sensitive to the bacteriocins. No inhibition of tested Gram-negative bacteria, some strains of Lactobacillus and of strains of Staphylococcus aureus was observed.All the in vitro conditions tested for the production of the bacteriocins (temperature, pH and NaCl), indicate that the strain of L. curvatus 54M16 is able to grow and to produce the antagonistic substances at pH 4.5 and in the presence of 4% NaCl. The strain has good acidifier capability and it is able to hydrolyse sarcoplasmic but not myofibrillar proteins, lipids and to reduce nitrates. Moreover it shown high values of SOD, while the aminopeptidase activity is restricted to whole cells that hydrolyse at high rates the amino acids l-arginine, l-valine, l-phenylalanine and l-lysine. The suitability of L. curvatus 54M16 as starter culture was assayed during sausage fermentation. Its use can improve the quality and safety of the traditional fermented sausages prepared without antimicrobial additives.

A comparison for acid production, proteolysis, autolysis and inhibitory properties of lactic acid bacteria from fresh and mature Feta PDO Greek cheese, made at three different mountainous areas

Isolates of NSLAB were obtained from fresh (58 isolates) and mature (38) Feta cheese made at household level in three different mountainous areas, in order to study the effect of the area of production on NSLAB composition and their technological characteristics. Results obtained by SDS-PAGE of whole-cell proteins indicated that the microflora of the fresh cheese was composed of either lactococci (areas 1, 2), or lactococci and enterococci (area 3). The NSLAB microflora of mature cheese was composed almost entirely of lactobacilli species, differing according to the area of production. Species allocation by the SDS-PAGE method was confirmed by sequencing representative strains. Lactococci of cheese made in area 1 exhibited a narrow spectrum of antibacterial activity compared to isolates from areas 2 and 3, while for lactobacilli from all three areas a similar spectrum was noticed. Lactococci from area 2 exhibited higher (P<0.05) mean acidifying activity than lactococci from area 1. The isolates from the three areas also differed in respect of their caseinolytic activity, with preferences towards β-CN (areas 1 and 2) or αs-CN (area 3). Mean proteolytic activity of lactococci from area 1 was stronger (P<0.05) than that of lactococci from area 2 and the same was observed for their mean aminopeptidase activity, as well as their extent of autolysis at pH5.1. Mean acidifying activity of lactobacilli after 6h was for strains of area 3>2=1. The strains from areas 1 and 3 degraded preferentially αs-CN, while a clear preference towards β-CN was noticed for strains of area 2; their mean proteolytic activity was for strains of area 1 higher (P<0.05) than strains from area 3. The above results suggest that cheeses from the three areas differ in species composition of NSLAB and their technological properties. Principal component analysis of results on acidifying and proteolytic activities as well as autolysis allowed the distinction of lactococci according to their derivation area enabling the selection of appropriate strains as starters for cheese production in each area.

Microbial population dynamics during spontaneous fermentation of Asparagus officinalis L. young sprouts

The aim of the present study was to assess the spontaneous fermentation of Asparagus officinalis L. young sprouts. For this purpose, asparagus fermentation was performed according to a traditional procedure originating from northern Greece. Young asparagus sprouts were cut, submerged in a brine solution (8 % NaCl) and placed in room temperature for fermentation to occur. Fermentation was monitored by measuring pH and total titratable acidity values as well as by qualitative and quantitative assessment of the microbiota dynamics. The latter was performed by classical microbiological techniques; clustering was performed by SDS-PAGE of whole cell proteins and rep-PCR and identification by sequencing of the 16S-rRNA gene. A culture-independent approach [PCR-denaturing gradient gel electrophoresis (DGGE)] was also applied in order to obtain a more integrated view of the microbiota dynamics. Lactic acid bacteria prevailed the fermentation forming a microbial consortium that was stable at species level; Lactobacillus sakei and Enterococcus faecium dominated until the 5th day while Weissella viridescens and W. cibaria dominated from the 7th day until the end of fermentation. Combination of SDS-PAGE with rep-PCR resulted in a very efficient clustering and differentiation also at sub-species level, revealing a succession at that level of all species throughout fermentation. On the other hand, application of PCR-DGGE was of limited usefulness.

Application of culture-dependent and culture-independent methods for the identification of Lactobacillus kefiranofaciens in microbial consortia present in kefir grains

The biological and technological characteristics of kefiran as well as its importance in grain integrity led us to analyze the microbial kefir grain consortium with focus on Lactobacillus kefiranofaciens. The presence of L. kefiranofaciens in the nine kefir grains studied was demonstrated by denaturing gradient gel electrophoresis. By culture dependent methods applying a methodology focused on the search of this species, 22 isolates with typical morphology were obtained and identified applying a combination of SDS-PAGE of whole cell proteins, (GTG)5-PCR and sequence analysis of the housekeeping gene encoding the α-subunit of bacterial phenylalanyl-tRNA synthase (pheS). This polyphasic approach allowed the reliable identification of 11 L. kefiranofaciens, 5 Lactobacillus paracasei, 4 Lactobacillus kefiri and 2 Lactobacillus parakefiri isolates. Isolated L. kefiranofaciens strains produced polysaccharide in strain-dependent concentrations and EPS produced by them also differed in the degree of polymerization. The isolation and accurate identification of L. kefiranofaciens is relevant taking into account the important role of this microorganism in the grain ecosystem as well as its potential application as starter in food fermentations.

Isolation of novel homopolysaccharide-producing lactic acid bacteria from Romanian raw milk and fermented dairy products

Traditionally fermented foods can be a rich source of diverse lactic acid bacteria (LAB) with interesting functional properties, such as exopolysaccharide (EPS) production. The objectives of this study were to map the mucoid and/or ropy LAB isolated from raw milk and traditionally fermented dairy products, collected in different regions of Romania, to study the species diversity within the samples and to further explore the EPS-producing capacity of the isolates. Seventy-three LAB strains were isolated and identified through (GTG)5-PCR genomic fingerprinting and SDS-PAGE of whole-cell proteins. Lactococcus lactis was the most frequently encountered species, followed by Lactobacillus plantarum, Leuconostoc spp., and Enterococcus spp. Nine strains produced homopolysaccharides (HoPS, glucose monomers), namely L. lactis 1.8; Leuc. citreum 1.10, 1.11, 1.12, 2.8, and 4.11; Leuc. mesenteroides 21.2; Leuc. pseudomesenteroides 20.6; and Weisella confusa/cibaria 38.2, six of them in the concentrations above 10 g/L, both in milk and MRS medium supplemented with sucrose. In all EPS, the glucose constituents were connected by different α-linkages, among which α-1,6-linkages were the most prevalent.

Detection and Identification of Vibrio Species Using Whole-Cell Protein Pattern Analysis

Outbreaks of foodborne diseases associated with Vibrio species such as V. parahaemolyticus, V. vulnificus, and V. cholerae frequently occur in countries having a dietary habit of raw seafood consumption. For rapid identification of different Vibrio species involved in foodborne diseases, whole-cell protein pattern analysis for 13 type strains of 12 Vibrio species was performed using SDS-PAGE analysis. Pathogenic Vibrio species such as V. parahaemolyticus, V. vulnificus, V. cholerae, V. alginolyticus, V. fluvialis, and V. mimicus were included in the 12 Vibrio species used in this study. Each of the 12 Vibrio species showed clearly specific band patterns of its own. Two different strains of V. parahaemolyticus showed two different SDS-PAGE wholecell protein patterns, giving the possibility of categorizing isolated strains in the same V. parahaemolyticus species into two subgroups. The 36 Vibrio isolates collected from sushi restaurants in Busan were all identified as V. parahaemolyticus by comparing their protein patterns with those of Vibrio type strains. The identified isolates were categorized into two different subgroups of V. parahaemolyticus. The whole-cell protein pattern analysis by SDS-PAGE can be used as a specific, rapid, and simple identification method for Vibrio spp. involved in foodborne diseases at the subspecies level.

Cupriavidus necator isolates are able to fix nitrogen in symbiosis with different legume species

The aim of the present study was to identify a collection of 35 Cupriavidus isolates at the species level and to examine their capacity to nodulate and fix N2. These isolates were previously obtained from the root nodules of two promiscuous trap species, Phaseolus vulgaris and Leucaena leucocephala, inoculated with soil samples collected near Sesbania virgata plants growing in Minas Gerais (Brazil) pastures. Phenotypic and genotypic methods applied for this study were SDS-PAGE of whole-cell proteins, and 16S rRNA and gyrB gene sequencing. To confirm the ability to nodulate and fix N2, the presence of the nodC and nifH genes was also determined, and an experiment was carried out with two representative isolates in order to authenticate them as legume nodule symbionts. All 35 isolates belonged to the betaproteobacterium Cupriavidus necator, they possessed the nodC and nifH genes, and two representative isolates were able to nodulate five different promiscuous legume species: Mimosa caesalpiniaefolia, L. leucocephala, Macroptilium atropurpureum, P. vulgaris and Vigna unguiculata. This is the first study to demonstrate that C. necator can nodulate legume species.

Probiotic and Technological Properties of Facultatively Heterofermentative Lactobacilli from Greek Traditional Cheeses

Nineteen isolates of facultatively heterofermentative lactobacilli from Feta, Graviera, and Kasseri cheeses were identified by SDS-PAGE of whole-cell proteins as L. paracasei subsp. paracasei (12 strains) and L. plantarum (7 strains) and differentiated at strain level by RAPD-PCR. Properties of technological interest, such as acidification ability, proteolytic activity, and enzyme activities, were also studied. The test strains exhibited a low acidification activity, with significant interstrain differences after growth in milk for 24 h. They were also characterized by different casein breakdown ability, with around 50% of them accumulating amino acids at low amounts in the milk. Lactobacilli isolates differed in respect of enzyme activities, with β-galactosidase being the strongest activity found. Their probiotic potential was evaluated with in vitro studies on the resistance to low pH, bile salts, and pancreatin. The isolates from Feta showed a better survival than those from Kasseri and Graviera at low pH and viable cells were detected even after 3 h at pH 2.0. All strains tolerated bile salts at 0.3% and retained viability in the presence of pancreatin at 0.1%. Different patterns of antibacterial activities were recorded. The strains inhibited preferentially LAB species and some of them clostridia, E. coli O44 and B. cereus. Distinguished strains are promising probiotic candidates as adjuncts and deserve further studies.

Differentiation of Lactococci from 2 Greek Cheeses with Protected Designation of Origin by Phenotypic Criteria and RAPD‐PCR

Seventy-six lactococci isolates from 2 protected designation of origin (PDO) cheeses were studied for their acidification ability, proteolytic activity, and inhibitory activities as well as their intraspecies characterization by randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). Fifty-two of them were characterized as Lactococcus lactis subsp. lactis by the SDS-PAGE of whole-cell proteins. The test strains increased the amount of acid in milk from 6 to 24 h as well as the quantities of amino acids on incubation for 4 d. The majority of the isolates degraded preferentially αs-casein. The isolates from Feta differed from those of Graviera Kritis in respect of β-casein degradation. This fragment was either not degraded or underwent a small degradation by lactococci from Feta. A stronger intensity of acidification for the isolates from Feta and a higher casein breakdown ability for those from Graviera Kritis were also recorded. Lactococci from Feta and Graviera Kritis inhibited, preferentially, the growth of Escherichia coli O157:H7, and Yersinia enterocolitica, respectively. A high heterogeneity among the isolates according to RAPD-PCR was determined, as well as grouping of the isolates according to their source of isolation. Selected isolates from each cheese could be used as starters to make either Feta or Graviera Kritis.

Rhizobium vallis sp. nov., isolated from nodules of three leguminous species

Four bacterial strains isolated from root nodules of Phaseolus vulgaris, Mimosa pudica and Indigofera spicata plants grown in the Yunnan province of China were identified as a lineage within the genus Rhizobium according to the analysis of 16S rRNA gene sequences, sharing most similarity with Rhizobium lusitanum P1-7(T) (99.1 % sequence similarity) and Rhizobium rhizogenes IAM 13570(T) (99.0 %). These strains also formed a distinctive group from the reference strains for defined species of the genus Rhizobium in a polyphasic approach, including the phylogenetic analyses of the 16S rRNA gene and housekeeping genes (recA, atpD, glnII), DNA-DNA hybridization, BOX-PCR fingerprinting, phenotypic characterization, SDS-PAGE of whole-cell proteins, and cellular fatty acid profiles. All the data obtained in this study suggested that these strains represent a novel species of the genus Rhizobium, for which the name Rhizobium vallis sp. nov. is proposed. The DNA G+C content (mol%) of this species varied between 60.9 and 61.2 (T(m)). The type strain of R. vallis sp. nov. is CCBAU 65647(T) ( = LMG 25295(T) =HAMBI 3073(T)), which has a DNA G+C content of 60.9 mol% and forms effective nodules on Phaseolus vulgaris.

Identification and distribution of Bacillus species in doenjang by whole-cell protein patterns and 16S rRNA gene sequence analysis

Many bacteria are involved in fermentation of doenjang and Bacillus species are known to perform significant roles. Although the SDS-PAGE technique has been frequently used for classification and identification of bacteria in various samples, there has been no investigation of the microbial diversity in doenjang. This study aims to investigate the identification and distribution of dominant Bacillus species in doenjang using SDS-PAGE profiles of whole cell proteins and 16S rDNA sequencing. SDS-PAGE of whole cell proteins of the reference Bacillus strains yielded differential banding patterns that could be considered to be highly specific fingerprints. Bacterial strains isolated from doenjang samples were grouped using whole cell protein patterns, which were confirmed by the analysis of 16S rDNA sequencing. B. subtilis was found to be the most dominant strain in most of the samples, and B. licheniformis and B. amyloliquefaciens were less frequently detected. The results obtained in this study showed that a combined identification method, SDS-PAGE patterns of whole cell proteins and subsequent 16S rDNA sequence analysis, could successfully identify Bacillus species isolated from doenjang.

Phylogenetic relationships and diversity of β-rhizobia associated with Mimosa species grown in Sishuangbanna, China

In order to investigate the genetic diversity of rhizobia associated with various exotic and invasive species in tropical mainland China, 116 bacterial isolates were obtained from Mimosa root nodules collected from Sishuangbanna and Yuanjiang districts of Yunnan province. Isolated rhizobia were characterized by RFLP analysis of 16S rRNA genes, SDS-PAGE of whole-cell proteins and BOX-PCR. Most of the isolated strains were identified as β-rhizobia belonging to diverse populations of Burkholderia and Cupriavidus, and the phylogenetic relationships of their 16S rRNA gene sequences showed that they were closely related to one of four β-rhizobia species: Burkholderia phymatum, B. mimosarum, B. caribensis or Cupriavidus taiwanensis. Additionally, among the 116 isolates, 53 different whole-cell SDS-PAGE profiles and 30 distinct BOX-PCR genotypic patterns were detected, which demonstrated the genetic and phenotypic diversity found within these Burkholderia and Cupriavidus strains. To the best of our knowledge, this is the first report that β-rhizobia are extant and possibly widespread on the Chinese mainland and nodulate easily with Mimosa plants. We also find it especially interesting that this appears to be the first report from mainland China of Cupriavidus symbionts of Mimosa. These records enrich our knowledge and understanding of the geographical distribution and diversity of these bacteria.

Diversity and high nitrogenase activity of endophytic diazotrophs isolated from Oryza rufipogon Griff.

Diversity and nitrogenase activity of endophytic diazotrophs colonized in the wild rice Oryza rufipogon Griff grown in Boluo, Huilai County in Guangdong Province and Lingshui County in Hainan Province were studied. Thirty-seven isolates obtained from Oryza rufipogon were identified as putative endophytic nitrogen-fixing bacteria by ARA (acetylene reduction assay) test and further confirmed by PCR amplification of nifH gene fragments. All obtained strains have ARA activity and the same sized nifH gene fragments. Above the similarity level of 80%, the obtained isolates were assigned as Group I to VIII by the clustering of IS-PCR fingerprints. The SDS-PAGE whole-cell protein patterns were similar to those of IS-PCR fingerprints. Components and contents of fatty acid methyl esters (FAMEs) were used to differentiate the representative strains (Ls13, Ls8, BL1, BL12, HL6, Ls4) from Group I to Group VI. The six representative strains showed significant difference in contents and components of cellular fatty acid methyl ester. 16S rDNA sequencing analysis showed that strains of Group I to VII were located in Enterobacteraceae (γ-proteobacteria). Strains of Group I and Group II were closely related to Klebsiella sp.; Strain Ls8 of Group II was a little far away from the genus of Pantoea (homology level 96% with Pantoea agglomerans), which may represent a new species or genus in Enterobacteraceae; Strains of Groups IV and V belonged to different Enterobacter sp.; Strain Ls4 and Ls 9 representing Group VI were close to Citrobacter amalonaticus with 98% sequence similarity; Strain Ls15 of Group VII showed 98% sequence identity with Pantoea sp.; Strains of Group VIII were assigned to the genus Ideonella (β-proteobacteria). Based on the above results, endophytic diazotrophs isolated from O. rufipogon showed great diversity and some diazotrophs showed high nitrogenase activity with 42.52 μmol/mL·h C2H4. Inoculation to rice tests indicated that the isolated endophytic diazotrophs significantly promoted the rice growth.

Enterobacter oryzae sp. nov., a nitrogen-fixing bacterium isolated from the wild rice species Oryza latifolia

Twelve facultatively anaerobic, endophytic diazotrophs were isolated from surface-sterilized roots of the wild rice species Oryza latifolia and characterized by phenotypic and molecular methods. Six isolates were grouped together as group A by phenotypic characters, and this grouping was confirmed by SDS-PAGE whole-cell protein patterns and insertion sequence-based PCR (IS-PCR) methods. Phylogenetic analysis of the 16S rRNA gene sequence indicated that group A, represented by strain Ola 51(T), is closely related to Enterobacter radicincitans D5/23(T) (98.9 % similarity, except that E. radicincitans D5/23(T) has a 70 bp insertion) and Enterobacter cloacae (98.0 % similarity to the type strain). rpoB gene sequence analysis also showed strain Ola 51(T) has the highest sequence similarity to E. radicincitans DSM 16656(T) (98.3 %), but supported the distinct position. Biological and biochemical tests, protein patterns, genomic DNA fingerprinting, antibiotic resistance and comparison of cellular fatty acids showed differences among group A, E. radicincitans DSM 16656(T) and E. cloacae ATCC 13047(T). DNA-DNA hybridization distinguished strain Ola 51(T) from closely phylogenetically related Enterobacter species. Based on these data, the novel species Enterobacter oryzae sp. nov. is proposed, with strain Ola 51(T) (=LMG 24251(T) =CGMCC 1.7012(T)) as the type strain.

Enterobacter oryzae sp. nov., a nitrogen-fixing bacterium isolated from the wild rice species Oryza latifolia

Twelve facultatively anaerobic, endophytic diazotrophs were isolated from surface-sterilized roots of the wild rice species Oryza latifolia and characterized by phenotypic and molecular methods. Six isolates were grouped together as group A by phenotypic characters, and this grouping was confirmed by SDS-PAGE whole-cell protein patterns and insertion sequence-based PCR (IS-PCR) methods. Phylogenetic analysis of the 16S rRNA gene sequence indicated that group A, represented by strain Ola 51T, is closely related to Enterobacter radicincitans D5/23T (98.9 % similarity, except that E. radicincitans D5/23T has a 70 bp insertion) and Enterobacter cloacae (98.0 % similarity to the type strain). rpoB gene sequence analysis also showed strain Ola 51T has the highest sequence similarity to E. radicincitans DSM 16656T (98.3 %), but supported the distinct position. Biological and biochemical tests, protein patterns, genomic DNA fingerprinting, antibiotic resistance and comparison of cellular fatty acids showed differences among group A, E. radicincitans DSM 16656T and E. cloacae ATCC 13047T. DNA–DNA hybridization distinguished strain Ola 51T from closely phylogenetically related Enterobacter species. Based on these data, the novel species Enterobacter oryzae sp. nov. is proposed, with strain Ola 51T (=LMG 24251T =CGMCC 1.7012T) as the type strain.

Rhizobium fabae sp. nov., a bacterium that nodulates Vicia faba

Six strains were isolated from root nodules of Vicia faba grown in Nanchang, Yifeng, Taihu, Huaibei, Bengbu and Lujiang, in the middle and lower reaches of the Yangtze River. According to phylogenetic analyses of 16S rRNA gene, atpD and recA sequences, these strains belong to the genus Rhizobium, with Rhizobium etli and Rhizobium leguminosarum as the closest related species. CCBAU 33202(T), a representative of these novel isolates, showed sequence similarity to its closest relatives R. etli CFN 42(T) and R. leguminosarum USDA 2370(T) of 99.5 and 99.1 % for the 16S rRNA gene, 91.9 and 91.9 % for atpD and 90.3 and 93.2 % for recA. The strains from this study could also be differentiated from R. etli CFN 42(T) and R. leguminosarum USDA 2370(T) by 16S-IGS RFLP and SDS-PAGE of whole-cell proteins, fatty acid profiles and several phenotypic characteristics. DNA-DNA hybridization yielded relatedness of 19 and 14-43 %, respectively, with R. etli CFN 42(T) and strains representing different biovars of R. leguminosarum. All data obtained in this study showed that these V. faba isolates belong to a novel species, for which the name Rhizobium fabae sp. nov. is proposed. The type strain, CCBAU 33202(T) (=LMG 23997(T) =JCM 14381(T)), was isolated from Nanchang.

Mesorhizobium gobiense sp. nov. and Mesorhizobium tarimense sp. nov., isolated from wild legumes growing in desert soils of Xinjiang, China

Twenty-four Mesorhizobium strains were isolated from desert soils in the Xinjiang region of China and were characterized by a polyphasic approach. These strains grouped into three clusters in IGS-RFLP, SDS-PAGE analysis of whole-cell proteins and BOX-PCR analysis, corresponding to genomic species V, VI and VII as found in a previous study. The results were supported by sequencing analyses of rrs, IGS, atpD and recA genes. Genospecies VII was most related to Mesorhizobium septentrionale, while genospecies V and VI were both most closely related to Mesorhizobium tianshanense, but were distinct from each other and from M. tianshanense. The DNA-DNA hybridization value between the representative strain CCBAU 83284 (genospecies VII) and the type strain of M. septentrionale was 90.1 %. Genospecies VII was thus defined as M. septentrionale. The DNA-DNA relatedness value for representative strains of genospecies V or VI with the related reference strains of recognized species were always lower than 60 %. Low values of DNA-DNA hybridization (32.79 %) between representative strains of genospecies V (CCBAU 83330(T)) and of VI (CCBAU 83306(T)) were also observed. Based upon these results, two novel species are proposed: Mesorhizobium gobiense sp. nov. represented by genospecies V (type strain, CCBAU 83330(T)=LMG 23949(T)=HAMBI 2974(T)) and Mesorhizobium tarimense sp. nov. represented by genospecies VI (type strain, CCBAU 83306(T)=LMG 24338(T)=HAMBI 2973(T)). Strain CCBAU 83278 grouped as the most peripheral member with genospecies VI in SDS-PAGE of whole-cell proteins and BOX-PCR analysis and in the phylogenetic tree of 16S-23S rRNA intergenic spacer (IGS) sequences. The results of analyses of rrs, atpD and recA gene sequences, as well as those of DNA-DNA hybridization studies, strongly supported the suggestion that this strain belonged to a species quite different from genospecies V and VI and from any other recognized species of the genus Mesorhizobium. As only one strain has been isolated to date, strain CCBAU 83278 was not proposed as a novel species in this study. Mesorhizobium gobiense sp. nov. and Mesorhizobium tarimense sp. nov. could be differentiated from each other as well as from recognized species of the genus Mesorhizobium on the basis of phenotypic characteristics. The symbiotic loci (nodC and nifH) of the two novel species formed two phylogenetic branches related to Mesorhizobium loti and M. tianshanense. The type strains of the two novel species were able to nodulate Glycyrrhiza uralensis, Lotus corniculatus, Oxytropis glabra and Robinia pseudoacacia but not Astragalus membranaceus, Leucaena leucocephala, Phaseolus vulgaris, Pisum sativum or Medicago sativa.

Characterization of lactic acid bacteria isolated from sourdoughs for Cornetto, a traditional bread produced in Basilicata (Southern Italy)

A total of 41 strains of lactic acid bacteria (LAB) isolated from durum wheat sourdoughs used to produce Cornetto di Matera bread, were identified by SDS-PAGE of whole cell proteins (WCP) and screened for acid production ability, antimicrobial activity and exopolysaccharide (EPS) production. The isolates were identified as Lactobacillus plantarum (49%), Leuconostoc mesenteroides (17%), Lactobacillus curvatus (15%), Lactobacillus paraplantarum (12%), Weissella cibaria (5%) and Lactobacillus pentosus (2%). Several strains of Lb. plantarum and Leuc. mesenteroides showed a high acid production ability. The antagonistic activity was tested using an agar-spot deferred antagonism assay against a set of five indicators. The species had different profiles of inhibition. Lb. plantarum had the largest spectrum of inhibition, while no isolates of W. cibaria and Leuc. mesenteroides showed antimicrobial activity. No strains had antimicrobial activity against Bacillus cereus. The inhibitory activity of five strains was confirmed to be sensitive to proteolytic enzymes and thus potentially due to bacteriocin production. All Leuc. mesenteroides and W. cibaria strains produced EPS from sucrose. Some Lb. plantarum and Lb. paraplantarum strains produced EPS from different sugars in solid media. EPS production in liquid media was different within the species, with the highest production in liquid media containing glucose and maltose. A defined strain starter culture (W. cibaria DBPZ1006, Lb. plantarum DBPZ1015 and S. cerevisiae MTG10) was selected on the basis of technological properties and tested in model sourdough fermentations.

Diversity of endophytic diazotrophs isolated fromBambusa blumeanain Guangdong province

AbstractEndophytic bacteria isolated from Guangdong bamboo (Bambusa blumeana) plants were obtained under aerobic and anaerobic cultural conditions. Using the acetylene reduction assay (ARA), 40 strains were identified as diazotrophs. Diazotrophic isolates were grouped into five clusters (I, II, III, IV and V) by SDS-PAGE whole-cell protein patterns. The analysis of full-length 16S rDNA sequences of the representative strains of each group indicated that the endophytic diazotrophs showed great diversity and belonged to the generaAzospirillum(α-subclass of proteobacteria),EscherichiaandPseudomonas(γ-subclass of proteobacteria), andAquaspirillum(β-subclass of proteobacteria).

Mesorhizobium albiziae sp. nov., a novel bacterium that nodulates Albizia kalkora in a subtropical region of China

A novel Mesorhizobium group associated with Albizia kalkora [Wang et al. (2006), Syst Appl Microbiol 29, 502-517] was further characterized. The seven strains in this group showed similar protein patterns and were different from defined Mesorhizobium species in SDS-PAGE of whole-cell proteins. The representative strain CCBAU 61158(T) formed a novel Mesorhizobium lineage in phylogenetic analyses of 16S rRNA, atpD, glnII and nifH genes. However, its nodC gene sequence was more similar to that of Rhizobium gallicum R602sp(T) than to those of Mesorhizobium species. DNA-DNA relatedness between CCBAU 61158(T) and reference strains of defined Mesorhizobium species was lower than 34.1 %. These results indicated that this Mesorhizobium group was a unique genomic species. The subtropical distribution, host origin, PCR-RFLP patterns of 16S rRNA genes, fatty acid profile and a series of phenotypic characteristics could be used as distinctive features of this group. This group is therefore proposed as a novel species, Mesorhizobium albiziae sp. nov., with CCBAU 61158(T) (=LMG 23507(T)=USDA 4964(T)) as the type strain. Strain CCBAU 61158(T) could form effective nodules on Albizia julibrissin, Glycine max, Leucaena leucocephala and Phaseolus vulgaris.