Beijing has many neighborhoods, some of which are new and others with a long history. In the case of some enclaves the name starts with the name of the originating province and the name ends in cun or "Village". For instance, Anhuicun or "Anhui Village" houses people from that room, Henancun or "Henan Village" has settlers from that region. Several ethnic enclaves house rural migrant workers based on their origin, such as Henancun and Zhejiangcun. Other ethnic enclaves consist of ethnic minorities who are established as permanent Beijing residents, including several Hui people settlements, such as Niujie and Madian,Wenfei Wang, Shangyi Zhou, Cindy Fan wrote that Hui people, despite being permanent Beijingers, are "highly segregated" from Han people "socially and spatially", they added that the survival of Hui neighborhoods in Beijing is "solely dependent on the existing Hui residents and communities" because the communities are "not as replenished by new migrants" and because Hui see themselves as Beijingers and their communities as having "more permanent meanings" compared to migrant worker communities.
Residents of the migrant worker enclaves support each other in looking for jobs and dealing with the local government. Inhabitants consider themselves "compatriots", a word equivalent to the English "homies". In the rural migrant worker communities there is a high turnover as members arrive for work and leave to go back to their hometowns; some residents work in family workshops and go to the city to sell their wares while others commute to work within the city. Most residents plan to return to their home lands and do not consider themselves to be from Beijing. Though the rural migrant workers are Han Chinese they are considered to be of a lower status because they are not permanent residents and because they have rural upbringings and low socioeconomic statuses, so each community, in the words of Wenfei Wang, Shangyi Zhou, Cindy Fan, "connotes a native place–based ethnicity distinct from the urbanites". During periods the Beijing government has attempted to dismantle ethnic villages in the periphery of Beijing.
In the 1990s the government made attempts to dismantle Zhejiangcun, including one time in 1995, had acted against Henancun and Xinjiangcun. While Uighurs, like the Hui, are Muslim, the Uighurs in Beijing had migrated there more than the Hui. Wenfei Wang, Shangyi Zhou, C. Cindy Fan, authors of "Growth and Decline of Muslim Hui Enclaves in Beijing," stated that the Beijing Uighur communities are "much smaller in size" compared to Hui communities. Geography of Beijing Deng, F. Frederick and Youqin Huang. "Uneven land reform and urban sprawl in China: the case of Beijing". Progress in Planning 61 211–236. Accepted October 27, 2003. Friedmann, John. China's Urban Transition. University of Minnesota Press, 2005. ISBN 1452907412, 9781452907413. Wang, Shangyi Zhou, C. Cindy Fan. "Growth and Decline of Muslim Hui Enclaves in Beijing". Eurasian Geography and Economics, 2002, 43, No. 2, pp. 104–122
Candidatus Carsonella ruddii is an obligate endosymbiotic Gamma Proteobacterium with one of the smallest genomes of any characterised bacteria. The species is an endosymbiont, present in all species of phloem sap-feeding insects known as psyllids; the endosymbionts occurs in a specialised structure known as the bacteriome. C. ruddii is not parasitic in its relationship with its host insect. It is therefore in the evolutionary process of becoming an organelle, similar to the mitochondria of eukaryotic cells that evolved from an endosymbiont. In 2006 the genome of Ca. C. ruddii strain Pv of the hackberry petiole gall psyllid, Pachypsylla venusta, was sequenced at RIKEN in Japan and the University of Arizona. It was shown that the genome consists of a circular chromosome of 159,662 base pairs and that it has a high coding density with many overlapping genes and reduced gene length; the number of predicted genes was 182 the lowest on record. In comparison, Mycoplasma genitalium, which has the smallest genome of any free-living organism, has a genome of 521 genes.
Numerous genes considered essential for life seem to be missing, suggesting that the species may have achieved organelle-like status. At the time of its sequencing, C. ruddii was thought to have the smallest genome of any characterized bacterial species. Nasuia deltocephalinicola is now considered to have the known smallest bacterial genome. C. Ruddii and related species appear to be undergoing gene loss. Scientific American – Tiny Genome May Reflect Organelle in the Making