Background : The very-preterm infant gut microbiota is increasingly explored due to its probable role in thedevelopment of life threatening diseases. Results of high-throughput studies validate and renew the interest inapproaches with lower resolution such as PCR-Temporal Temperature Gel Electrophoresis (TTGE) for the follow-upof dominant microbiota dynamics. We report here an extensive longitudinal study of gut colonization in verypreterm infants. We explored by 16S rDNA-based PCR-TTGE a total of 354 stool specimens sampled during routinemonitoring from the 1stto the 8thweek of life in 30 very pre-term infants born before 30 weeks of gestational age. Results : Combining comparison with a diversity ladder and sequencing allowed affiliation of 50 Species-LevelOperational Taxonomic Units (SLOTUs) as well as semi-quantitative estimation of Operational Taxonomic Units (OTUs).Coagulase-negative staphylococci, mainly theStaphylococcus epidermidis, was found in all the infants during the studyperiod and was the most represented (75.7% of the SLOTUs) from the first days of life. Enterococci, present in 60% ofthe infants were early, highly represented and persistent colonizers of the premature gut. LaterEnterobacteriaceaeandthe genusClostridiumappeared and were found in 10 (33%) and 21 infants (70%), respectively. We showed a highrepresentation of Veillonellain more than a quarter of the infants and being able to persistently colonize premature gut. The genera Anaerococcus, Aquabacterium,Bacillus, Bifidobacterium,Corynebacterium, Micrococcus, Oceanobacillus, Propionibacterium, Pseudomonas, Rothia, Sarcina, Sneathiaand Streptococcuswere observed as transient or persistentcolonizers, each genus being found in a minority of infants. Conclusions : Despite low resolution, PCR-TTGE remains complementary to high-throughput sequencing-basedapproaches because it allows the follow-up of dominant bacteria in gut microbiota in a large longitudinal cohorts ofpreterm neonates. We described the development of pre-term gut microbiota that should be now replaced regardingthe functional role of major OTUs.