The pga gene cluster in Aggregatibacter actinomycetemcomitans is necessary for the development of natural competence in Ca(2+) -promoted biofilms

Natural competence is the ability of bacteria to incorporate extracellular DNA into their genomes. This competence is affected by a number of factors, including Ca(2+) utilization and biofilm formation. As bacteria can form thick biofilms in the presence of extracellular Ca(2+) , the additive effects of Ca(2+) -promoted biofilm formation on natural competence should be examined. We evaluated natural competence in Aggregatibacter actinomycetemcomitans, an important periodontal pathogen, in the context of Ca(2+) -promoted biofilms, and examined whether the pga gene cluster, required for bacterial cell aggregation, is necessary for competence development. The A. actinomycetemcomitans cells grown in the presence of 1 mm CaCl2 exhibited enhanced cell aggregation and increased levels of cell-associated Ca(2+) . Biofilm-derived cells grown in the presence of Ca(2+) exhibited the highest levels of natural transformation frequency and enhanced expression of the competence regulator gene, tfoX. Natural competence was enhanced by the additive effects of Ca(2+) -promoted biofilms, in which high levels of pga gene expression were also detected. Mutation of the pga gene cluster disrupted biofilm formation and competence development, suggesting that these genes play a critical role in the ability of A. actinomycetemcomitans to adapt to its natural environment. The Ca(2+) -promoted biofilms may enhance the ability of bacteria to acquire extracellular DNA.

[Factors allowing continuous working of female nurses in the People's Republic of China--survey of 15 hospitals in 5 areas]

PURPOSE

Few investigations have been conducted on working, childcare and home education among female nurses (nurses) in the People's Republic of China (P.R. of China). The purpose of this study was to clarify the factors allowing continued working of female nurses.

METHODS

The subjects were nurses from 15 hospitals in 3 provinces and 2 autonomous areas. They were surveyed by questionnaire regarding their childcare and home education. In was distributed by the Ministry of Health in the P.R. of China and the data were collected between February and April in 1996.

RESULTS

A total of 4,284 (80.0%) questionnaires were collected. 1. About 60% of the nurses began working when they were 15 to 19 years old. The average length of service was 13.9 years. 2. Their professional position correlated directly with their years of service. 3. 4.3% of them had not continued working. 4. The nurses entrust their children to day-care institutions (61.2%) or grandparents (22.3%) during the daytime, and to the father (66.3%) or the grandparents (19.5%) during the night. 5. 17.6% of them have experienced being away from home for more than one month due to their job. 6. 66.8% of the nurses have experienced more than one month official trip, and had children under 14 years old at the time. They entrusted their children to day-care institutions (34.1%), to the father (29.2%) and grandparents (25.3%) during the official trip.

CONCLUSIONS

In summary, most nurses are employed when they are young and go on working as nurses. It is possible for them to continue their work after marriage, childbirth, and while they are bringing up their children. The high rate of working woman, sufficient nursery schools and family cooperation in housework can be pointed out as main factors that enable them to continue their work.

[Childcare and home education in families of female nurses in the People's Republic of China--survey of 15 hospitals in 5 areas]

PURPOSE

The purpose of this study was to investigate the actual conditions of childcare and home education among families of female nurses in the P. R. of China.

METHODS

The subjects were nurses from 15 hospitals in 3 provinces and 2 autonomous areas. They were surveyed by questionnaire regarding their childcare and home education. It was distributed by the Ministry of Health in the P. R. of China and data were collected between February and April in 1996.

RESULTS

A total of 4284 (80.0%) questionnaires were collected. 1. The age of the subjects was between 18 and 62 years old with a mean of 32.9 +/- 9.0 (SD) years 71.4% of them had husbands, whose ages were between 23 and 71 years old, the mean age being 38.3 +/- 8.4 (SD) years. The family types were 63.2% nuclear family and 33.7% extended family, with 3.1% being single. 65.1% of the subjects had children, whose mean number was 1.1 +/- 0.4 (SD). Firstborn children were 49.9% girls and 50.1% boys. 2. The most popular method of infant nutrition was breast-feeding, utilized by 60.1%. The highest rate (67.8%) was in the age group of 25 to 29 years old (P < 0.01). 3. The practice of "swaddling" (wrapping the child so as not to allow movement) was more common in the over 40 year old age group than the under 40 year old group (P < 0.01). Swaddling-practice showed significant differences by area. 4. The rates for children who helped with housework were 50.3% for girls and 46.7% for boys. 5. A number of children between 7 and 18 years old were studying English privately. 6. The greatest expectation of the subjects, for their children aged between 7 and 18 years old, was to study.

CONCLUSIONS

1. Infant nutrition showed significant differences between generations, and swaddling-practice differed with the generation and the area. 2. Although girls help their parents more than boys in Japan, boys and girls equally helped their parents in the P. R. of China. 3. Concerning the topics of private learning and parents expectations, the results were similar to those in Japan.