Mutualistic associations of aphids and prokaryotes: biology of the genus buchnera.
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Journal Article↗
Biomedical subjects
L Baumann
Publications and source records attributed to L Baumann.
Genetics, physiology, and evolutionary relationships of the genus Buchnera: intracellular symbionts of aphids.
Evolutionary studies suggest that 200-250 million years ago an aphid ancestor was infected with a free-living eubacterium. The latter became established within aphid cells. Host and endosymbiont (genus Buchnera) became interdependent and unable to survive without each other. The growth of Buchnera became integrated with that of the aphids, which acquired the endosymbionts from their mothers before birth. Speciation of host lineages was paralleled by divergence of associated endosymbiont lineages, resulting in parallel evolution of Buchnera and aphids. Present day Buchnera retains many of the properties of its free-living ancestor, containing genes for proteins involved in DNA replication, transcription, and translation, as well as chaperonins and proteins involved in secretion, energy-yielding metabolism, and amino acid biosynthesis. Some of these processes are also observed in isolated endosymbiont cells. Genetic and physiological studies indicate that Buchnera can synthesize methionine, cysteine, and tryptophan and supply these amino acids to the aphid host. In the case of some fast-growing species of aphids, the overproduction of tryptophan by Buchnera involves plasmid-amplification of the gene coding for anthranilate synthase, the first enzyme of the tryptophan biosynthetic pathway. These recent studies provide a beginning in our understanding of Buchnera and its role in the endosymbiosis with aphids.
Animals↗
Amplification of trpEG: adaptation of Buchnera aphidicola to an endosymbiotic association with aphids.
Survival of aphids is dependent on an association with a prokaryotic endosymbiont (Buchnera aphidicola) found in specialized cells within the aphid body cavity. Recent nutritional and physiological studies have indicated that one of the functions of the endosymbionts is the synthesis of tryptophan [Douglas, A. E. & Prosser, W. A. (1992) J. Insect Physiol. 38, 565-568]. B. aphidicola resembles in many of its properties free-living prokaryotes. An adaptation to an endosymbiosis involving the overproduction of tryptophan would necessitate alterations that modify the effect of regulatory systems that in free-living organisms function to reduce enzyme activity under conditions of excess tryptophan. We have cloned and sequenced the genes for B. aphidicola trpEG encoding anthranilate synthase, the first enzyme of the tryptophan biosynthetic pathway, which in free-living bacteria is feedback-inhibited by tryptophan. Amino acid sequence comparisons indicate that the B. aphidicola enzyme has all of the key residues involved in allosteric feedback inhibition. Evidence is presented indicating that trpEG is present as four tandem repeats on a circular plasmid. Relative to B. aphidicola trpDC(F)BA (the chromosomal genes coding for the remaining enzymes of the tryptophan biosynthetic pathway) trpEG is amplified 14- to 15-fold. These findings suggest that the effect of inhibition by accumulated tryptophan may be overcome by overproduction of anthranilate synthase. Our results demonstrate the acquisition of a new property (gene amplification) as an adaptation to an endosymbiotic association in which B. aphidicola overproduces tryptophan for the aphid host.
Amino Acid Sequence↗
[Atrophodermia linearis Moulin. A new disease picture, following the Blaschko lines].
Many different congenital and acquired skin diseases are seen along Blaschko's lines. In 1992, Moulin et al. [40] described five patients affected with a new clinical entity characterized by acquired atrophic band-like skin lesions showing hyperpigmentation. We report on a further patient with this skin disease. Characteristic features are hyperpigmented atrophoderma arranged in a pattern following the lines of Blaschko, with no preceding inflammation and no subsequent induration or scleroderma. The lesions usually appear during childhood or adolescence, but sometimes in young adults. For this skin disease we propose the term 'linear atrophoderma of Moulin'.
Adult↗
Detection of Buchnera, the primary prokaryotic endosymbiont of aphids, using the polymerase chain reaction.
Members of the genus Buchnera constitute a distinct prokaryotic lineage containing the primary endosymbionts of aphids (Homoptera: Aphidoidea). Using synthetic oligonucleotides in conjunction with the polymerase chain reaction, we propose three approaches for the identification of members of this genus. The first is based on unique sequences within rrs (gene coding for 16S ribosomal RNA). The second is based on a different and unique organization of the ribosomal RNA operons of Buchnera and the close proximity of aroE upstream of rrl (gene coding for 23S rRNA). The third is based on the linkage relationship of argS which is upstream of rrs. Validation of these three approaches requires their more extensive application.
Animals↗
Growth Kinetics of the Endosymbiont Buchnera aphidicola in the Aphid Schizaphis graminum.
The aphid Schizaphis graminum is dependent on its prokaryotic endosymbiont, Buchnera aphidicola. As a means of determining B. aphidicola numbers during the growth cycle of the aphid we have used the quantitative PCR to measure the number of copies of rrs (the gene coding for 16S rRNA, which is present as one copy in the B. aphidicola genome). In addition we have measured the aphid wet weight and the DNA and protein content. The results indicate an approximately parallel (23- to 31-fold) increase of these properties during the period of aphid growth. A 1-day-old aphid (24 mug [wet weight]) has 0.2 x 10 copies of rrs, while a 9-day-old aphid (497 mug [wet weight]) has 5.6 x 10 copies. The coupling of endosymbiont and aphid growth is consistent with the requirement of the endosymbiont for growth and reproduction of the aphid.
Journal Article↗
Pediatric living-related and cadaveric liver transplantation: a single center experience.
Living-related liver transplantation is becoming more commonplace worldwide in the treatment of end-stage liver disease in the pediatric age group. Our LRD experience has resulted in patient and graft survival rates comparable to our cadaveric donor recipients. The incidence and severity of acute rejection episodes were similar. This differs from the clear immunologic advantage of living-related donation in kidney transplantation. It may, however, reflect the relatively small numbers in our LRD group. Overall, however, the technical complications are manageable with early intervention, yielding acceptable results.
Adult↗
Buchnera aphidicola (a prokaryotic endosymbiont of aphids) contains a putative 16S rRNA operon unlinked to the 23S rRNA-encoding gene: sequence determination, and promoter and terminator analysis.
The aphid Schizaphis graminum is dependent on an association with Buchnera aphidicola, an eubacterial endosymbiont located in specialized host cells. Past studies have indicated that Escherichia coli is the closest known relative of the endosymbiont which has many genetic attributes of free-living bacteria. In order to obtain information on the properties of highly expressed genes, we have chosen for study the single-copy rrs (gene encoding 16S rRNA) of B. aphidicola. A 4.4-kb DNA fragment was cloned into E. coli and the nucleotide (nt) sequence determined. Several ORFs were identified; the order of genes was argS-rrs-ORF1-rnh-dnaQ. ArgS, RNase H and DnaQ had 36-57% amino acid (aa) identity to the homologous proteins of E. coli. B. aphidicola rrs appears to be part of an operon consisting of a putative promoter, rrs and two inverted repeats resembling Rho-independent terminators. Comparisons of the sequences of argS-rrn DNA fragments from endosymbionts of six additional aphid species indicated conservation of sequences corresponding to a single -35 (TTGACA) and -10 (TGTAAT) promoter region, as well as boxA (sequence involved in antitermination) and boxC. The B. aphidicola argS-rrn DNA fragments from endosymbionts from seven species of aphids had promoter activities in E. coli which ranged from 6 to 135% of that observed with a comparable DNA fragment of E. coli rrnB. Similarly, the putative B. aphidicola terminator was functional in E. coli. In most eubacteria, the rRNA-encoding genes are arranged in the order, 16S, 23S, 5S, and are part of a single operon.(ABSTRACT TRUNCATED AT 250 WORDS)
Amino Acid Sequence↗
Development of the living-related donor liver transplant program at the Texas Medical Center: initial results and surgical complications.
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Female↗
Sequence analysis of an aphid endosymbiont DNA fragment containing rpoB (beta-subunit of RNA polymerase) and portions of rplL and rpoC.
The aphid Schizaphis graminum is dependent on an association with a prokaryotic endosymbiont (Buchnera aphidicola). The nucleotide (nt) sequence of a 5040 base pair (bp) DNA fragment of B. aphidicola, homologous to the rplL-rpoB-rpoC portion of the Escherichia coli beta operon, was determined. The DNA coded for the terminal 35 amino acids of RplL (large ribosomal subunit protein L7/L12), the complete RpoB (beta-subunit of RNA polymerase), and the first 209 amino acids of RpoC (beta'-subunit of RNA polymerase). The deduced sequences of B. aphidicola RplL, RpoB, and RpoC were 71, 84, and 91% identical, respectively, to the homologous proteins of E. coli. The sequences of two portions of the intergenic region between rplL and rpoB were nearly identical in both B. aphidicola and E. coli. One sequence constituted an inverted repeat that could be an RNase III-messenger RNA processing site; the other sequence preceded RpoB. A compilation of the codon usage for RpoB, RpoC, and other B. aphidicola proteins indicated a major preference for A or T in the first and third positions, a result consistent with the low guanine plus cytosine (G + C) content of the DNA of this organism.
Amino Acid Sequence↗
Nonoperative management of major blunt renal trauma in children: in-hospital morbidity and long-term followup.
The management of 26 children with major renal injury secondary to blunt trauma was reviewed. Emergency computerized tomography (CT) was performed in all instances. Injury ranged from parenchymal laceration to vascular avulsion. Early surgical exploration was done in 5 children due to hemodynamic instability, renal pedicle injury or suspected malignancy. The remaining 21 children were observed. Of these children 5 had associated intra-abdominal organ injuries. The average length of hospitalization was 13.4 days and the average intensive care unit stay was 6.9 days. A third of the children were transfused with an average 10.8 cc/kg. of packed red cells. Ten patients (47.6%) had febrile episodes that lasted an average of 3 days. No foci of infection other than bladder urine were identified and there were no infected perirenal collections. In 2 children ureteral stents were placed cystoscopically. Exploration was performed in 1 child for delayed hemorrhage 2 months after hospital discharge. Followup CT was available in 15 patients and all kidneys functioned, including 3 with residual focal scarring, 2 with parenchymal calcifications and 1 with a cyst. Eleven patients were evaluated clinically at least 1 year after injury and all were asymptomatic, while 1 child had mild diastolic hypertension. In conclusion, nonoperative management results in an excellent long-term outcome in the majority of cases. In-hospital morbidity is minimal and early surgical exploration should be reserved for those with hemodynamic instability or renal pedicle injury. Immediate CT is an invaluable aid in categorizing and managing these patients.
Adolescent↗
Evidence for the establishment of aphid-eubacterium endosymbiosis in an ancestor of four aphid families.
Aphids (superfamily Aphidoidea) contain eubacterial endosymbionts localized within specialized cells (mycetocytes). The endosymbionts are essential for the survival of the aphid hosts. Sequence analyses of the 16S rRNAs from endosymbionts of 11 aphid species from seven tribes and four families have indicated that the endosymbionts are monophyletic. Furthermore, phylogenetic relationships within the symbiont clade parallel the relationships of the corresponding aphid hosts. Our findings suggest that this endocytobiotic association was established in a common ancestor of the four aphid families with subsequent diversification into the present species of aphids and their endosymbionts.
Animals↗
Bacillus sphaericus as a mosquito pathogen: properties of the organism and its toxins.
In the course of sporulation, Bacillus sphaericus produces an inclusion body which is toxic to a variety of mosquito larvae. In this review we discuss the general biology of this species and concentrate on the genetics and physiology of toxin production and its processing in the midgut of the larval host. The larvicide of B. sphaericus is unique in that it consists of two proteins of 51 and 42 kDa, both of which are required for toxicity to mosquito larvae. There is a low level of sequence similarity between these two proteins, which differ in their sequences from all the other known insecticidal proteins of Bacillus thuringiensis. Within the midgut the 51- and 42-kDa proteins are processed to proteins of 43 and 39 kDa, respectively. The conversion of the 42-kDa protein to a 39-kDa protein results in a major increase in toxicity; the significance of the processing of the 51-kDa protein is not known. In contrast to the results with mosquito larvae, the 39-kDa protein is alone toxic for mosquito-derived tissue culture-grown cells, and this toxicity is not affected by the 51-kDa protein or its derivative, the 43-kDa protein. Comparisons of larvae from species which differ in their susceptibility to the B. sphaericus toxin indicate that the probable difference resides in the nature of the target sites of the epithelial midgut cells and not in uptake or processing of the toxin. A similar conclusion is derived from experiments involving tissue culture-grown cells from mosquito species which differ in their susceptibility to the B. sphaericus toxin.
Amino Acid Sequence↗
The 42- and 51-kilodalton mosquitocidal proteins of Bacillus sphaericus 2362: construction of recombinants with enhanced expression and in vivo studies of processing and toxicity.
After site-directed mutagenesis, the genes coding for the 42- and 51-kilodalton (kDa) mosquitocidal proteins of Bacillus sphaericus 2362 were placed under the regulation of the aprE (subtilisin) promoter of the Bacillus subtilis vector pUE (a derivative of pUB18). The levels of expression of the gene products in B. subtilis DB104 and B. sphaericus 718 were assessed by bioassays with larvae of Culex pipiens and by Western immunoblots. The results indicated that a higher amount of protein was produced in B. subtilis DB104. Electron microscopic examination of B. subtilis DB104 and B. sphaericus 718 containing the 42- and 51-kDa proteins indicated that amorphous inclusions accumulated in the former species and that crystals identical in appearance to that found in B. sphaericus 2362 were produced in the latter. Strains producing only the 42- or the 51-kDa protein were not toxic to larvae of C. pipiens. A mixture of both strains, a single strain producing both proteins, or a fusion of the 51- and the 42-kDa proteins was toxic. The amount of B. subtilis DB104 containing the 42- and the 51-kDa proteins necessary to kill 50% of the larvae of C. pipiens was 5.6 ng (dry weight) of cells per ml. This value was significantly lower than that for B. sphaericus 2362 (14 ng [dry weight] per ml). Larvae consuming purified amorphous inclusions containing the 42-kDa protein degraded this protein this protein to primarily 39- and 24-kDa peptides, whereas inclusions with the 51-kDa protein were primarily degraded to a protein of 44 kDa. Past studies involving purified proteins from B. sphaericus 2362 indicate an associate of toxicity with the 39-kDa peptide. The results presented here suggest that the 44-kDa degradation product of the 51-kDa protein may also be required for toxicity.
Animals↗
Construction by site-directed mutagenesis of a 39-kilodalton mosquitocidal protein similar to the larva-processed toxin of Bacillus sphaericus 2362.
After ingestion of the parasporal crystals of Bacillus sphaericus, mosquito larvae process the 42-kilodalton (kDa) toxin to a protein of 39 kDa, which has an increased toxicity (A. H. Broadwell and P. Baumann, Appl. Environ. Microbiol. 53:1333-1337, 1987). A similar activation is performed by trypsin and chymotrypsin. Using site-directed mutagenesis, we have constructed derivatives of the 42-kDa toxin with a deletion of 10 amino acids at the N terminus and deletions of 7, 17, or 20 amino acids at the C terminus. Toxicity for mosquito larvae was retained upon deletion of 7 or 17 amino acids but was lost upon deletion of 20 amino acids. Evidence is presented indicating that the protein containing deletions of 10 amino acids at the N terminus and 17 amino acids at the C terminus (corresponding to potential chymotrypsin cleavage sites) is similar to the 39-kDa protein produced in mosquito larvae or by digestion with chymotrypsin. Digestion with trypsin appears to generate a protein lacking 16 or 19 amino acids from the N terminus and 7 amino acids from the C terminus. As is the case with the recombinant-made 42-kDa protein, toxicity of its derivatives is dependent on the presence of a 51-kDa protein which is a component of the parasporal crystal of B. sphaericus 2362.
Amino Acid Sequence↗
[Genital chlamydia infections and extrauterine pregnancy].
Serum samples of 217 patients with ectopic pregnancy (e.p.) and of 152 women with intrauterine pregnancy (i.u.p.) were examined for their antibody content to chlamydia trachomatis by means of the indirect immunofluorescence technique. In 81% of the sera of patients with e.p., antibody could be detected, while patients with i.u.p. revealed antibody in 39%. Titres greater than or equal to 1:128 were found in 49% (e.p.) and in only 11% (i.u.p.) respectively; so they possess a high diagnostic value. These results show significant differences in the behaviour of antibodies in both groups of patients and are illustrated in 2 charts. Anamnestic data showed 54% of the patients with e.p. (i.e. adnexitis 23%, gonorrhea 12.3%, previous e.p. 18.4%); the mean age was 29 years. Affected tubes may lose their physiological function, possibly resulting in an ectopic pregnancy. The level of antibody in the serum remains stabile for many years, this enables a retrospective diagnosis of chlamydial infections. An early diagnosis and treatment, including the partners, represent the best way for prevention of complications.
Adult↗
Expression in Bacillus subtilis of the 51- and 42-kilodalton mosquitocidal toxin genes of Bacillus sphaericus.
A 3,080-base-pair KpnI-HindIII DNA fragment from Bacillus sphaericus 2362 coding for 51- and 42-kilodalton mosquitocidal proteins was cloned into Bacillus subtilis DB104 by using the vector pUB18. In B. subtilis these proteins were not detected during vegetative growth but were expressed during sporulation at levels comparable to those found in B. sphaericus.
Bacillus↗
[The capacity of Ureaplasma urealyticum, Mycoplasma hominis and seven other Mycoplasma species for hemadsorption, sperm adsorption, hemolysis and peroxide formation].
Searching for potential virulence markers of Ureaplasma (U.) urealyticum and Mycoplasma (M.) hominis, simple laboratory methods were used to detect strain specific properties. Haemadsorption, sperm adsorption, haemolysis, and peroxide formation were tested on clinical isolates and type strains of U. urealyticum and M. hominis in comparison to reference strains of seven other Mycoplasma species. In contrast to M. bovis, M. gallisepticum and M. pulmonis, all strains of M. hominis and U. urealyticum failed to adsorb human spermatozoa and erythrocytes from five vertebrate species to their colonies. Unexpectedly, colonies of M. arthritidis PG 6 adsorbed both human erythrocytes and spermatozoa. Using various methods, the known haemolytic and peroxide activities of the reference strains could be confirmed. None of the U. urealyticum strains tested demonstrated lysis of human or ovine erythrocytes or peroxide production. On the other hand, 76 of 108 isolates of M. hominis showed an alpha'- or beta-haemolysis of different degree. However, this phenomenon could not be reproduced in all cases and it was not attributable to the activity of a peroxide. None of the methods used in this study were found to be suitable for detection of possible virulence factors of U. urealyticum or M. hominis.
Adsorption↗