Limits...
Genomic and physiological variability within Group II (non-proteolytic) Clostridium botulinum.

Stringer SC, Carter AT, Webb MD, Wachnicka E, Crossman LC, Sebaihia M, Peck MW - BMC Genomics (2013)

Bottom Line: These results were compared with characteristics determined from physiological tests.However, these two subsets did not differ strongly in minimum growth temperature or maximum NaCl concentration for growth.No relationship was found between tellurite resistance and toxin type despite all the tested type B and type F strains carrying tehB, while the sequence was absent or diverged in all type E strains.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Food Research (IFR), Norwich Research Park, Colney, Norwich NR4 7UA, UK. sandra.stringer@ifr.ac.uk

ABSTRACT

Background: Clostridium botulinum is a group of four physiologically and phylogenetically distinct bacteria that produce botulinum neurotoxin. While studies have characterised variability between strains of Group I (proteolytic) C. botulinum, the genetic and physiological variability and relationships between strains within Group II (non-proteolytic) C. botulinum are not well understood. In this study the genome of Group II strain C. botulinum Eklund 17B (NRP) was sequenced and used to construct a whole genome DNA microarray. This was used in a comparative genomic indexing study to compare the relatedness of 43 strains of Group II C. botulinum (14 type B, 24 type E and 5 type F). These results were compared with characteristics determined from physiological tests.

Results: Whole genome indexing showed that strains of Group II C. botulinum isolated from a wide variety of environments over more than 75 years clustered together indicating the genetic background of Group II C. botulinum is stable. Further analysis showed that strains forming type B or type F toxin are closely related with only toxin cluster genes targets being unique to either type. Strains producing type E toxin formed a separate subset. Carbohydrate fermentation tests supported the observation that type B and F strains form a separate subset to type E strains. All the type F strains and most of type B strains produced acid from amylopectin, amylose and glycogen whereas type E strains did not. However, these two subsets did not differ strongly in minimum growth temperature or maximum NaCl concentration for growth. No relationship was found between tellurite resistance and toxin type despite all the tested type B and type F strains carrying tehB, while the sequence was absent or diverged in all type E strains.

Conclusions: Although Group II C. botulinum form a tight genetic group, genomic and physiological analysis indicates there are two distinct subsets within this group. All type B strains and type F strains are in one subset and all type E strains in the other.

Show MeSH

Related in: MedlinePlus

Physiological characteristics of strains of Group II C. botulinum. The minimum temperature and maximum NaCl concentration at which growth was observed, the minimum concentration of tellurite required to prevent growth and the ability to ferment selected carbohydrates was tested on strains representing different clades. Acid production was measured in a PY basal medium with 10 g l-1 added carbohydrate. A carbohydrate was considered to be fermented if the final pH was more than 0.5 units less than inoculated medium in the absence of carbohydrate. A pH reduction of 0.5-1.0 units was noted as acid production (+) and >1.0 was noted as strong acid production (++). For details of the hierarchical clustering dendrogram see Figure 5.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3672017&req=5

Figure 6: Physiological characteristics of strains of Group II C. botulinum. The minimum temperature and maximum NaCl concentration at which growth was observed, the minimum concentration of tellurite required to prevent growth and the ability to ferment selected carbohydrates was tested on strains representing different clades. Acid production was measured in a PY basal medium with 10 g l-1 added carbohydrate. A carbohydrate was considered to be fermented if the final pH was more than 0.5 units less than inoculated medium in the absence of carbohydrate. A pH reduction of 0.5-1.0 units was noted as acid production (+) and >1.0 was noted as strong acid production (++). For details of the hierarchical clustering dendrogram see Figure 5.

Mentions: The minimum growth temperature and maximum NaCl concentration allowing growth in the test conditions, and the results of the tellurite MIC assay and the carbohydrate fermentation tests are shown in Figure 6. Although there is variability between the strains, differences in the minimum growth temperature, maximum NaCl concentration and tellurite resistance were relatively small compared to the range in bacteria as a whole. The range was 2.5°C in growth temperature and 1.7% in NaCl concentration. The mean MIC of tellurite was also similar for all strains, ranging from 10–40 mg ml-1. Bacteria are considered to be sensitive to tellurite if the MIC is 1-2 mg l-1 and to be resistant at 1000 mg l-1[18]. All the strains were of intermediate sensitivity. No relationship was observed between tellurite resistance and toxin type or Clade with the mean MIC of strains producing type B, E or F toxin being 25, 27 and 26 mg l-1 respectively. Similarly, there did not appear to be a clear relationship between toxin type and minimum growth temperature or maximum NaCl concentration for growth. In the conditions used in this test, all strains grew at 6.5°C and the lowest temperature at which growth was observed was 4.0°C. The median minimum growth temperature was 5.0°C for strains of each toxin type. On average the type E strains had a slightly higher tolerance to NaCl than type B and type F strains, with a mean maximum NaCl concentration of 4.1% and 3.9% respectively, but there was considerable overlap between the strains of each toxin type.


Genomic and physiological variability within Group II (non-proteolytic) Clostridium botulinum.

Stringer SC, Carter AT, Webb MD, Wachnicka E, Crossman LC, Sebaihia M, Peck MW - BMC Genomics (2013)

Physiological characteristics of strains of Group II C. botulinum. The minimum temperature and maximum NaCl concentration at which growth was observed, the minimum concentration of tellurite required to prevent growth and the ability to ferment selected carbohydrates was tested on strains representing different clades. Acid production was measured in a PY basal medium with 10 g l-1 added carbohydrate. A carbohydrate was considered to be fermented if the final pH was more than 0.5 units less than inoculated medium in the absence of carbohydrate. A pH reduction of 0.5-1.0 units was noted as acid production (+) and >1.0 was noted as strong acid production (++). For details of the hierarchical clustering dendrogram see Figure 5.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672017&req=5

Figure 6: Physiological characteristics of strains of Group II C. botulinum. The minimum temperature and maximum NaCl concentration at which growth was observed, the minimum concentration of tellurite required to prevent growth and the ability to ferment selected carbohydrates was tested on strains representing different clades. Acid production was measured in a PY basal medium with 10 g l-1 added carbohydrate. A carbohydrate was considered to be fermented if the final pH was more than 0.5 units less than inoculated medium in the absence of carbohydrate. A pH reduction of 0.5-1.0 units was noted as acid production (+) and >1.0 was noted as strong acid production (++). For details of the hierarchical clustering dendrogram see Figure 5.
Mentions: The minimum growth temperature and maximum NaCl concentration allowing growth in the test conditions, and the results of the tellurite MIC assay and the carbohydrate fermentation tests are shown in Figure 6. Although there is variability between the strains, differences in the minimum growth temperature, maximum NaCl concentration and tellurite resistance were relatively small compared to the range in bacteria as a whole. The range was 2.5°C in growth temperature and 1.7% in NaCl concentration. The mean MIC of tellurite was also similar for all strains, ranging from 10–40 mg ml-1. Bacteria are considered to be sensitive to tellurite if the MIC is 1-2 mg l-1 and to be resistant at 1000 mg l-1[18]. All the strains were of intermediate sensitivity. No relationship was observed between tellurite resistance and toxin type or Clade with the mean MIC of strains producing type B, E or F toxin being 25, 27 and 26 mg l-1 respectively. Similarly, there did not appear to be a clear relationship between toxin type and minimum growth temperature or maximum NaCl concentration for growth. In the conditions used in this test, all strains grew at 6.5°C and the lowest temperature at which growth was observed was 4.0°C. The median minimum growth temperature was 5.0°C for strains of each toxin type. On average the type E strains had a slightly higher tolerance to NaCl than type B and type F strains, with a mean maximum NaCl concentration of 4.1% and 3.9% respectively, but there was considerable overlap between the strains of each toxin type.

Bottom Line: These results were compared with characteristics determined from physiological tests.However, these two subsets did not differ strongly in minimum growth temperature or maximum NaCl concentration for growth.No relationship was found between tellurite resistance and toxin type despite all the tested type B and type F strains carrying tehB, while the sequence was absent or diverged in all type E strains.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Food Research (IFR), Norwich Research Park, Colney, Norwich NR4 7UA, UK. sandra.stringer@ifr.ac.uk

ABSTRACT

Background: Clostridium botulinum is a group of four physiologically and phylogenetically distinct bacteria that produce botulinum neurotoxin. While studies have characterised variability between strains of Group I (proteolytic) C. botulinum, the genetic and physiological variability and relationships between strains within Group II (non-proteolytic) C. botulinum are not well understood. In this study the genome of Group II strain C. botulinum Eklund 17B (NRP) was sequenced and used to construct a whole genome DNA microarray. This was used in a comparative genomic indexing study to compare the relatedness of 43 strains of Group II C. botulinum (14 type B, 24 type E and 5 type F). These results were compared with characteristics determined from physiological tests.

Results: Whole genome indexing showed that strains of Group II C. botulinum isolated from a wide variety of environments over more than 75 years clustered together indicating the genetic background of Group II C. botulinum is stable. Further analysis showed that strains forming type B or type F toxin are closely related with only toxin cluster genes targets being unique to either type. Strains producing type E toxin formed a separate subset. Carbohydrate fermentation tests supported the observation that type B and F strains form a separate subset to type E strains. All the type F strains and most of type B strains produced acid from amylopectin, amylose and glycogen whereas type E strains did not. However, these two subsets did not differ strongly in minimum growth temperature or maximum NaCl concentration for growth. No relationship was found between tellurite resistance and toxin type despite all the tested type B and type F strains carrying tehB, while the sequence was absent or diverged in all type E strains.

Conclusions: Although Group II C. botulinum form a tight genetic group, genomic and physiological analysis indicates there are two distinct subsets within this group. All type B strains and type F strains are in one subset and all type E strains in the other.

Show MeSH
Related in: MedlinePlus