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							Scientometrics of Horizontal Gene Transfer Research during 1991-2005
                                      De-Cheng Yu1#, Wen-Ta Chiu2,3 and Yuh-Shan Ho1*
                                1Bibliometric
                                            Centre, Taipei Medical University - Wan-Fang Hospital
                          2Graduate Institute of Injury Prevention and Control, Taipei Medical University
                           3Department of Neurosurgery, Taipei Medical University Wan Fang Hospital

Introduction
Horizontal gene transfer or lateral gene transfer, is the collective name for processes that permit the exchange of DNA among organisms of
different species. Traditional thought was that microorganisms evolved clonally, passing genes from mother to daughter cells with little or no
exchange of DNA among diverse species. Recent studies of microbial genomes have shown that genomes contain genes that are closely
related to a number of different prokaryotes, sometimes to phylogenetically very distantly related ones. The horizontal movement of gene
play an important role in the evolution of microorganisms. Our purpose was to study the horizontal gene transfer research based on 1,172
documents published in Science Citation Index (SCI)-indexed periodicals between 1991 and 2005. These documents were analyzed and
evaluated according to publication distribution and were used to determine the quantitative characteristics of horizontal gene transfer
research.
Methods                                                                                                               Table 1. Publication activity of top ten countries
Documents used in this study were based on the databases of the SCI which                                             Country       SP SP% CPP CP CP% CPP P P% CPP
was accessed from the ISI Web of Science. Horizontal gene transfer was
used as keywords to search titles, abstracts, and keywords.                                                           USA           225          34    11 105   46    14 330 38    12
Results
                                                                                                                      Germany           94       14 6.8 60      27    21 154 18    12
Table 2. Major characteristics of the research             P: No. of articles                                         UK                49       7.5 6.4 51     23    18 100 11    12
                                                           PG: Total pages
Year P         PG        PG/P AU      AU/P NR       NR/P                                                              France            39       6.0   11 43    19    23 82 9.3    17
                                                           AU: No. of authors
1991      12        88    7.3   51     4.3   390      33   NR: Cited reference
                                                                                                                      Japan             42       6.4 6.6 16     7.1   34 58 6.6    14
                                                           count
1992      12    140        12   38     3.2   515      43   SP: single country                                         Canada            23       3.5 5.7 23     10    6.8 46 5.2 6.3
                                                           publications
1993      17    167       9.8   60     3.5   702      41   CP: international                                          Spain             18       2.8 5.3 25     11    25 43 4.9    17
1994      26    282        11   82     3.2   1765     68   collaboration
                                                           publications                                               Switzerland       16       2.4 6.1 17     7.5   35 33 3.8    21
1995      30    315        11   121    4.0   1503     50   CPP: 3 year (including                                     Netherlands 12             1.8 8.2 19     8.4   36 31 3.5    25
                                                           publish year) citation per
1996      34    302       8.9   107    3.1   1506     44   publication                                                Sweden            20       3.1 8.2   9    4.0   4.6 29 3.3   7
1997      36    374        10   270    7.5   2028     56
                                                                                     Figure 1:Conmulative number of publication
1998      57    523       9.2   211    3.7   3067     54
                                                               Cumulative number of publications




                                                                                                   1000
1999      70    764        11   231    3.3   4749     68                                            900                   Cumulative number of publications
                                                                                                    800                   1991-1994 Exponential model
2000      85   1029        12   405    4.8   4858     57
                                                                                                    700                   1994-1999 Logarithmic model
2001     111   1273        11   437    3.9   5926     53                                                                  1999-2005 Logarithmic model
                                                                                                    600
2002     114   1124       9.9   482    4.2   5872     52                                            500
2003     157   1671        11   634    4.0   8708     55                                            400
                                                                                                    300
2004     168   1743        10   704    4.2   9411     56
                                                                                                    200
2005     241   2542        11 1150     4.8 13675      57
                                                                                                    100
Total 1170 12337           11 4983     4.3 64675      55                                              0
                                                                                                          0   1   2   3    4    5   6        7    8    9 10 11 12 13 14 15 16
Conclusions                                                                                                                         Years since 1991
 Ten document types were found in the total of 1,172 documents published in 255 journals.
 USA has highest publication (38%) with 12 of citation per publications and followed distantly by United Kingdom.
 The G7 industrial countries (USA, Japan, Germany, UK, France, Italy, and Canada) represent a share of corresponding authors of 72%
  of world articles and 83% citations.
 Thirty-seven percent of all articles were published in journals which listed in the category of Microbiology.
 The most frequently used author keyword in articles was ‘horizontal gene transfer’ (47%), and followed by ‘evolution’ (7%), ‘phylogeny’
  (5.9%), ‘gene transfer’ (4.8%), and ‘escherichia coli’ (3.7%).
 The most productive corresponding institute was the University of Wurzburg at Germany with 14 articles and 7.36 of citation per articles.
 6.8% of all articles were published in Journal of Bacteriology with impact factor 4.146.
 There were 16% articles never be cited since it was published. 7.3% articles was cited once and 5.5% articles was cited 2 times.