Basic Types of Life

The main conflict In the species discussion may be summarized as follows: the population geneticist is mainly Interested in gene flow and, therefore, has to prefer a biospecies concept. On the other hand, the practicing taxonomist and the palaeontologist are mainly interested in similarity and, hence, have to use a morphological species concept. This conflict is fundamental and cannot easily be resolved. It is often stated that higher levels of classification are even more problematic than the species definition. Using a genetical criterion based on Interspecific hybridization, it is suggested that a systematic category above the genus level may be defined rather objectively: two organisms belong to the same basic type If (I) they are able to hybridize or (ii) they have hybridized with the same third organism. In principle It Is possible to check experimentally by artificial insemination or artificial pollination if two biparental individuals belong to the same basic type. The basic type category thus may prove to be open to empirical validation. Advantages and problems of this basic type criterion are discussed. A general summary follows on a few basic types of the plant and animal kingdom that have been described. Based on rather limited data it appears to emerge that (i) the basic type criterion can be applied successfully in animal as well as plant taxonomy, (Ii) a clear gap of overall similarity Is found between different basic types, (iii) within basic types a variety of mlcroevolutionary processes may help to understand speciation, and (iv) the distribution of characters across different species of the same basic type may be discussed under the hypothetical assumption of a large hidden variation potential harboured by a genetically complex ancestral population. It must be emphasized that only 14 basic types have been described to date. This number is too low to provide for a reliable basis of generalization. Therefore, the basic type concept is only suggested to serve as a preliminary working hypothesis

Insecticidal genes of Yersinia spp.: taxonomical distribution, contribution to toxicity towards Manduca sexta and Galleria mellonella, and evolution

<p>Abstract</p> <p>Background</p> <p>Toxin complex (Tc) proteins termed TcaABC, TcdAB, and TccABC with insecticidal activity are present in a variety of bacteria including the yersiniae.</p> <p>Results</p> <p>The <it>tc </it>gene sequences of thirteen <it>Yersinia </it>strains were compared, revealing a high degree of gene order conservation, but also remarkable differences with respect to pseudogenes, sequence variability and gene duplications. Outside the <it>tc </it>pathogenicity island (<it>tc</it>-PAI^<it>Ye</it>) of <it>Y. enterocolitica </it>strain W22703, a pseudogene (<it>tccC2'</it>/<it>3'</it>) encoding proteins with homology to TccC and similarity to tyrosine phosphatases at its C-terminus was identified. PCR analysis revealed the presence of the <it>tc</it>-PAI^{<it>Ye </it>}and of <it>tccC2'</it>/<it>3'</it>-homologues in all biotype 2–5 strains tested, and their absence in most representatives of biotypes 1A and 1B. Phylogenetic analysis of 39 TccC sequences indicates the presence of the <it>tc</it>-PAI^{<it>Ye </it>}in an ancestor of <it>Yersinia</it>. Oral uptake experiments with <it>Manduca sexta </it>revealed a higher larvae lethality of <it>Yersinia </it>strains harbouring the <it>tc</it>-PAI^{<it>Ye </it>}in comparison to strains lacking this island. Following subcutaneous infection of <it>Galleria mellonella </it>larvae with five non-human pathogenic <it>Yersinia </it>spp. and four <it>Y. enterocolitica </it>strains, we observed a remarkable variability of their insecticidal activity ranging from 20% (<it>Y. kristensenii</it>) to 90% (<it>Y. enterocolitica </it>strain 2594) dead larvae after five days. Strain W22703 and its <it>tcaA </it>deletion mutant did not exhibit a significantly different toxicity towards <it>G. mellonella</it>. These data confirm a role of TcaA upon oral uptake only, and suggest the presence of further insecticidal determinants in <it>Yersinia </it>strains formerly unknown to kill insects.</p> <p>Conclusion</p> <p>This study investigated the <it>tc </it>gene distribution among yersiniae and the phylogenetic relationship between TccC proteins, thus contributing novel aspects to the current discussion about the evolution of insecticidal toxins in the genus <it>Yersinia</it>. The toxic potential of several <it>Yersinia </it>spp. towards <it>M. sexta </it>and <it>G. mellonella </it>demonstrated here for the first time points to insects as a natural reservoir for yersiniae.</p

Comparative Bioinformatics and Experimental Analysis of the Intergenic Regulatory Regions of Bacillus cereus hbl and nhe Enterotoxin Operons and the Impact of CodY on Virulence Heterogeneity

Bacillus cereus is a food contaminant with greatly varying enteropathogenic potential. Almost all known strains harbor the genes for at least one of the three enterotoxins Nhe, Hbl, and CytK. While some strains show no cytotoxicity, others have caused outbreaks, in rare cases even with lethal outcome. The reason for these differences in cytotoxicity is unknown. To gain insight into the origin of enterotoxin expression heterogeneity in different strains, the architecture and role of 5' intergenic regions (5' IGRs) upstream of the nhe and hbl operons was investigated. In silico comparison of 142 strains of all seven phylogenetic groups of B. cereus sensu lato proved the presence of long 5' IGRs upstream of the nheABC and hblCDAB operons, which harbor recognition sites for several transcriptional regulators, including the virulence regulator PIcR, redox regulators ResD and Fnr, the nutrient-sensitive regulator CodY as well as the master regulator for biofilm formation SinR. By determining transcription start sites, unusually long 5' untranslated regions (5' UTRs) upstream of the nhe and hbl start codons were identified, which are not present upstream of cytK-1 and cytK-2. Promoter fusions lacking various parts of the nhe and hbl 5' UTR in B. cereus INRA C3 showed that the entire 331 bp 5' UTR of nhe is necessary for full promoter activity, while the presence of the complete 606 bp hbl 5' UTR lowers promoter activity. Repression was caused by a 268 bp sequence directly upstream of the hbl transcription start. Luciferase activity of reporter strains containing nhe and hbl 5' IGR lux fusions provided evidence that toxin gene transcription is upregulated by the depletion of free amino acids. Electrophoretic mobility shift assays showed that the branched-chain amino acid sensing regulator CodY binds to both nhe and hbl 5' UTR downstream of the promoter, potentially acting as a nutrient responsive roadblock repressor of toxin gene transcription. PIcR binding sites are highly conserved among all B. cereus sensu lato strains, indicating that this regulator does not significantly contribute to the heterogeneity in virulence potentials. The CodY recognition sites are far less conserved, perhaps conferring varying strengths of CodY binding, which might modulate toxin synthesis in a strain-specific manner

High Deleterious Genomic Mutation Rate in Stationary Phase of Escherichia coli

In natural habitats, bacteria spend most of their time in some form of growth arrest. Little is known about deleterious mutations in such stages, and consequently there is limited understanding of what evolutionary events occur. In a deleterious mutation accumulation experiment in prolonged stationary phase of Escherichia coli, about 0.03 slightly deleterious mutations were observed per genome per day. This is over an order of magnitude higher than extrapolations from fast-growing cells, but in line with inferences from observations in adaptive stationary phase mutation experiments. These findings may affect understanding of bacterial evolution and the emergence of bacterial pathogenicity

The Mutation Glu151Asp in the B-Component of the Bacillus cereus Non-Hemolytic Enterotoxin (Nhe) Leads to a Diverging Reactivity in Antibody-Based Detection Systems

The ability of Bacillus cereus to cause foodborne toxicoinfections leads to increasing concerns regarding consumer protection. For the diarrhea-associated enterotoxins, the assessment of the non-hemolytic enterotoxin B (NheB) titer determined by a sandwich enzyme immunoassay (EIA) correlates best with in vitro cytotoxicity. In general, the regulation of enterotoxin expression of B. cereus is a coordinately-regulated process influenced by environmental, and probably also by host factors. As long as these factors are not completely understood, the currently-applied diagnostic procedures are based on indirect approaches to assess the potential virulence of an isolate. To date, sandwich EIA results serve as a surrogate marker to categorize isolates as either potentially low or highly toxic. Here, we report on a single amino acid exchange in the NheB sequence leading to an underestimation of the cytotoxic potential in a limited number of strains. During the screening of a large panel of B. cereus isolates, six showed uncommon features with low sandwich EIA titers despite high cytotoxicity. Sequence analysis revealed the point-mutation (Glu)151(Asp) in the potential binding region of the capture antibody. Application of this antibody also results in low titers in an indirect EIA format and shows variable detection intensities in Western-immunoblots. A commercially-available assay based on a lateral flow device detects all strains correctly as NheB producers in a qualitative manner. In conclusion, isolates showing low NheB titers should additionally be assayed in an indirect EIA or for their in vitro cytotoxicity to ensure a correct classification as either low or highly toxic

Cereulide synthetase gene cluster from emetic Bacillus cereus: Structure and location on a mega virulence plasmid related to Bacillus anthracis toxin plasmid pXO1

BACKGROUND: Cereulide, a depsipeptide structurally related to valinomycin, is responsible for the emetic type of gastrointestinal disease caused by Bacillus cereus. Recently, it has been shown that this toxin is produced by a nonribosomal peptide synthetase (NRPS), but its exact genetic organization and biochemical synthesis is unknown. RESULTS: The complete sequence of the cereulide synthetase (ces) gene cluster, which encodes the enzymatic machinery required for the biosynthesis of cereulide, was dissected. The 24 kb ces gene cluster comprises 7 CDSs and includes, besides the typical NRPS genes like a phosphopantetheinyl transferase and two CDSs encoding enzyme modules for the activation and incorporation of monomers in the growing peptide chain, a CDS encoding a putative hydrolase in the upstream region and an ABC transporter in the downstream part. The enzyme modules responsible for incorporation of the hydroxyl acids showed an unusual structure while the modules responsible for the activation of the amino acids Ala and Val showed the typical domain organization of NRPS. The ces gene locus is flanked by genetic regions with high homology to virulence plasmids of B. cereus, Bacillus thuringiensis and Bacillus anthracis. PFGE and Southern hybridization showed that the ces genes are restricted to emetic B. cereus and indeed located on a 208 kb megaplasmid, which has high similarities to pXO1-like plasmids. CONCLUSION: The ces gene cluster that is located on a pXO1-like virulence plasmid represents, beside the insecticidal and the anthrax toxins, a third type of B. cereus group toxins encoded on megaplasmids. The ces genes are restricted to emetic toxin producers, but pXO1-like plasmids are also present in emetic-like strains. These data might indicate the presence of an ancient plasmid in B. cereus which has acquired different virulence genes over time. Due to the unusual structure of the hydroxyl acid incorporating enzyme modules of Ces, substantial biochemical efforts will be required to dissect the complete biochemical pathway of cereulide synthesis

Differenzierung probiotischer Bakterien

Die Fourier-Transform-Infrarot-(FTIR)-Spektroskopie ist prinzipiell in der Lage, Mikroorganismen auf Stammesebene zu trennen und zu differenzieren. Das Projekt hat zum Inhalt, bestehende FT-IR-Datenbanken um handelsübliche probiotische Futterzusatzstoffe zu erweitern. Nach der erfolgreichen Erarbeitung einer Datenbank zur sicheren Differenzierung von ubiquitären und probiotischen B. cereus-Stämmen wurden die Datenbanken um probiotische Sporenbildner der Spezies B. subtilis und B. licheniformis sowie um probiotische Milchsäurebakterien (Enterococcus, Lactobacillus, Pediococcus) erweitert. Alle probiotischen Stämme lassen sich sicher von ubiquitär vorkommenden Mikrooganismen der gleichen Spezies trennen, zumeist gelingt auch die Differenzierung der Probiotika untereinander. Diese einfache, preiswerte, schnelle und dennoch exakte Methode stellt einen enormen Fortschritt für die Futtermittelmikrobiologie dar

Growth and Fatty Acid Composition of Marine Microalga Nannochloropsis SP in Medium Enriched with Magnesium

Micro-algae are to be an attractive way to produce bio-diesel due to high photosynthetic yields and lipid accumulation in cells. This high productivity combined with possibility to uptake CO2 stimulated its utilization as a biological mitigation method of CO2, at once as an alternative renewable source of energy. Growth characteristics and chemical composition of micro-algae can be altered by culture environment. Nutrient sufficiency,included magnesium element (Mg2+) is important factors on overall biochemical composition. In study, Nannochloropsis sp was cultivated in Erlenmeyer 250 ml containing 200 ml f/2 medium. There are three groups of treatment with different levelof magnesium (Mg2+), i.e. 0 (M0); 0.1mgL-1 (M1); and 1.0 mgL-1 (M2). All treatment was designed triplicate in batch system. Culture was then aerated continuously with sterile atmospheric air (1.5 L.min-1). Cells were harvested on 25th day after inoculation and analyzed. Data showed that Chlorophyll-a increased linearly with time and maximum at 18th days of growth period, i.e. 23.57; 26.44; and 27.74mgL-1, for M0; M1; and M2,respectively. Chlorophyll-a content decreased significantly when pH dropped to 5-6.Enrichment with Mg2+ increased the chlorophyll-a content 12.2-17.7%. Dry cell reached 375-400mgL-1 in all treatment. Lipid content of Nannochloropsis sp in control (M0) is 55.3%, higher than M1 and M2. Saturated fatty acid tends to increase from 80.70 (M0)to 96.70 (M1) and 94.53% (M2). Fatty acid of M0 and M1 was composed dominantly by palmitic acid (C16:0), i.e. 49.19-70.75% total fatty acids. Meanwhile, M2 treatment was dominantly by lauric acid (C12:0), i.e. 32.98%

Interprofessional collaboration in nursing homes (interprof): A grounded theory study of general practitioner experiences and strategies to perform nursing home visits

Background: Interprofessionalism, considered as collaboration between medical professionals, has gained prominence over recent decades and evidence for its impact has grown. The steadily increasing number of residents in nursing homes will challenge medical care and the interaction across professions, especially nurses and general practitioners (GPS). The nursing home visit, a key element of medical care, has been underrepresented in research. This study explores GP perspectives on interprofessional collaboration with a focus on their visits to nursing homes in order to understand their experiences and expectations. This research represents an aspect of the interprof study, which explores medical care needs as well as the perceived collaboration and communication by nursing home residents, their families, GPS and nurses. This paper focusses on GPS' views, investigating in particular their visits to nursing homes in order to understand their experiences. Methods: Open guideline-interviews covering interprofessional collaboration and the visit process were conducted with 30 GPS in three study centers and analyzed with grounded theory methodology. GPS were recruited via postal request and existing networks of the research partners. Results: Four different types of nursing home visits were found: visits on demand, periodical visits, nursing home rounds and ad-hoc-decision based visits. We identified the core category "productive performance" of home visits in nursing homes which stands for the balance of GPŚ individual efforts and rewards. GPS used different strategies to perform a productive home visit: preparing strategies, on-site strategies and investing strategies. Conclusion: We compiled a theory of GPS home visits in nursing homes in Germany. The findings will be useful for research, and scientific and management purposes to generate a deeper understanding of GP perspectives and thereby improve interprofessional collaboration to ensure a high quality of care

Interprofessional collaboration in nursing homes (interprof): A grounded theory study of general practitioner experiences and strategies to perform nursing home visits

Background: Interprofessionalism, considered as collaboration between medical professionals, has gained prominence over recent decades and evidence for its impact has grown. The steadily increasing number of residents in nursing homes will challenge medical care and the interaction across professions, especially nurses and general practitioners (GPS). The nursing home visit, a key element of medical care, has been underrepresented in research. This study explores GP perspectives on interprofessional collaboration with a focus on their visits to nursing homes in order to understand their experiences and expectations. This research represents an aspect of the interprof study, which explores medical care needs as well as the perceived collaboration and communication by nursing home residents, their families, GPS and nurses. This paper focusses on GPS' views, investigating in particular their visits to nursing homes in order to understand their experiences. Methods: Open guideline-interviews covering interprofessional collaboration and the visit process were conducted with 30 GPS in three study centers and analyzed with grounded theory methodology. GPS were recruited via postal request and existing networks of the research partners. Results: Four different types of nursing home visits were found: visits on demand, periodical visits, nursing home rounds and ad-hoc-decision based visits. We identified the core category "productive performance" of home visits in nursing homes which stands for the balance of GPŚ individual efforts and rewards. GPS used different strategies to perform a productive home visit: preparing strategies, on-site strategies and investing strategies. Conclusion: We compiled a theory of GPS home visits in nursing homes in Germany. The findings will be useful for research, and scientific and management purposes to generate a deeper understanding of GP perspectives and thereby improve interprofessional collaboration to ensure a high quality of care