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A T Thomas

Publications and source records attributed to A T Thomas.

9 recordsLinked to original sources
PubMed2000

DNA-independent transport of plasmid primase protein between bacteria by the I1 conjugation system.

The ColIb-P9 (IncI1)-encoded conjugation system supports transfer of the plasmid T-strand plus hundreds of molecules of the Sog polypeptides determined by the plasmid primase gene. Here, we report that Sog primase is abundantly donated to the recipient cell from cells carrying a non-transferable ColIb plasmid deleted of the nic site essential for DNA export. Such DNA-independent secretion of Sog primase is typical of authentic conjugation, both in being blocked when the recipient cell specifies the entry exclusion function of ColIb and in requiring the thin I1 pilus encoded by the ColIb pil system under the mating conditions used. It is proposed that Sog polypeptides form a complex with the ColIb T-strand during conjugation and aid DNA transport through processive secretion of the proteins into the recipient cell. Functional and genetic relationships between the ColIb conjugation system and other type IV secretion pathways are discussed.

Conjugation, Genetic↗
PubMed1999

Transient transcriptional activation of the Incl1 plasmid anti-restriction gene (ardA) and SOS inhibition gene (psiB) early in conjugating recipient bacteria.

The ardA gene of the enterobacterial plasmid CollbP-9 acts to alleviate restriction of DNA by type I systems, while psiB inhibits induction of the bacterial SOS response. Both genes are transferred early in a round of bacterial conjugation as part of the plasmid leading region. We report here that ardA and psiB are transcribed transiently after their conjugative transport into the recipient cell. Transcript levels, monitored by competitive reverse transcription-polymerase chain reaction (RT-PCR) amplification of RNA templates, started to increase about 5 min after the initiation of conjugation in a cell population and probably before the first round of plasmid transfer was completed. Genetic evidence is given that the expression of ardA and psiB is activated when the genes enter the recipient cell on the transferring plasmid strand. It is proposed that these and other leading region genes function to promote the establishment of the immigrant plasmid in the new host and are expressed by transcription from promoters active only in single-stranded DNA.

Bacterial Proteins↗
PubMed1996

Distribution of restriction enzyme recognition sequences on broad host range plasmid RP4: molecular and evolutionary implications.

IncP alpha plasmids, exemplified by RP4, are remarkable for their broad host range. They contain strikingly few cleavage sites for many commonly used type II restriction enzymes but an overabundance of sites for certain enzymes that target G + C-rich sequences. To identify factors responsible for these distributions, the recently compiled nucleotide sequence of RP4 was analysed to determine the frequency of tetra- and hexanucleotide motifs in the 49 kb plasmid backbone. This is defined as the sectors encoding basic plasmid functions. The overabundant restriction targets in RP4 are concentrated in the backbone and contain overlapping copies of CGGC/GCCG, identified as the most abundant tetranucleotide motif in the plasmid. Motif frequencies in the RP4 backbone are shown to be similar to those in Pseudomonas aeruginosa, a natural host of RP4, with the notable exception that a number of 6-bp palindromes are underrepresented in the plasmid. It is proposed that 6-bp palindromes were counterselected as type II restriction enzyme recognition sequences. Conjugative transfer of RP4 and R751 (IncP beta) is unusually sensitive to restriction compared to enterobacterial plasmids of the IncFII and IncI1 groups, implying that IncP plasmids experienced particularly strong selection for loss of restriction targets. Pseudomonas spp. of rRNA homology group I specify many type II restriction enzymes that target 6-bp palindromes and are candidates for the evolutionary hosts of IncP alpha plasmids.

Base Composition↗
PubMed1992

Evasion of type I and type II DNA restriction systems by IncI1 plasmid CoIIb-P9 during transfer by bacterial conjugation.

Transmission of unmodified plasmid CoIIb-P9 by bacterial conjugation is markedly resistant to restriction compared with transfer by transformation. One process allowing evasion of type I and II restriction systems involves conjugative transfer of multiple copies of the plasmid. A more specialized evasion mechanism requires the Ard (alleviation of restriction of DNA) system encoded by CoIIb. The ard gene is transferred early in conjugation and specifically alleviates DNA restriction by all known families of type I enzyme, including EcoK. CoIIb has no effect on EcoK modification but this activity is impaired by multicopy recombinant plasmids supporting overexpression of ard. Genetic evidence shows that Ard protects CoIIb from EcoK restriction following conjugative transfer and that this protection requires expression of the gene on the immigrant plasmid. It is proposed that carriage of ard facilitates transfer of CoIIb between its natural enterobacterial hosts and that the route of DNA entry is important to the restriction-evasion mechanism.

Conjugation, Genetic↗
PubMed1989

Autologous blood transfusion.

Autologous blood transfusion is emerging as a popular option in patients undergoing elective procedures. Predeposit and perioperative autotransfusion, the two major types of autologous transfusion, can be performed safely in a wide variety of conditions and in patients of all ages. We discuss the risks and benefits and outline the minimal requirements of donor-patients. Autologous blood transfusion is a safe and effective method of providing blood products. It is the safest transfusion practice.

Blood Transfusion, Autologous↗
PubMed1968

Insulinoma.

Explore the source record for details and available documents.

Adenoma, Islet Cell↗
PubMedDate not supplied

Work process redesign at Vanderbilt University Medical Center's Transfusion Service.

Work process redesign is an effective tool to assist laboratories in identifying areas for improvement. This article presents the experiences and results of Vanderbilt University Medical Center's Transfusion Service in undergoing a work process redesign project to reduce costs and increase growth potential. Opportunities for improvement were identified, and processes were redesigned to enhance efficiencies and increase workload capacity. Areas where opportunities for improvement were identified included work-flow, work process, personnel usage, task delegation, information transfer, physical layout, and communication. The thorough review and redesign of the work processes resulted in a greater demonstrated workload capacity of 381% for pretransfusion testing (antibody screens ABO/D typing, and immediate-spin crossmatches), using no additional FTEs.

Academic Medical Centers↗