Low genomic diversity in tropical oceanic N2-fixing cyanobacteria.

High levels of genomic and allelic microvariation have been found in major marine planktonic microbial species, including the ubiquitous open ocean cyanobacterium, Prochlorococcus marinus. Crocosphaera watsonii is a unicellular cyanobacterium that has recently been shown to be important in oceanic N2 fixation and has been reported from the Atlantic and Pacific oceans in both hemispheres, and the Arabian Sea. In direct contrast to the current observations of genomic variability in marine non-N2-fixing planktonic cyanobacteria, which can range up to >15% nucleotide sequence divergence, we discovered that the marine planktonic nitrogen-fixing cyanobacterial genus Crocosphaera has remarkably low genomic diversity, with <1% nucleotide sequence divergence in several genes among widely distributed populations and strains. The cultivated C. watsonii WH8501 genome sequence was virtually identical to DNA sequences of large metagenomic fragments cloned from the subtropical North Pacific Ocean with <1% sequence divergence even in intergenic regions. Thus, there appears to be multiple strategies for evolution, adaptation, and diversification in oceanic microbial populations. The C. watsonii genome contains multiple copies of several families of transposases that may be involved in maintaining genetic diversity through genome rearrangements. Although genomic diversity seems to be the rule in many, if not most, marine microbial lineages, different forces may control the evolution and diversification in low abundance microorganisms, such as the nitrogen-fixing cyanobacteria.

Relationship among respondent ethnicity, ethnic identity, acculturation, and homeless status on a homeless population's functional status.

This study investigated the relationship of homeless status, ethnic identity, respondent ethnicity (African American, Latino, Native American, and Anglo), and Latino, Anglo, and Mexican American orientation on the functional impairment (Behavior and Symptom Identification Scale, BASIS-32; S. V. Eisen, 1996) of 355 homeless men and women who were interviewed in Pomona, California. Multivariate analyses of variance results indicated that respondent ethnicity was related to several BASIS-32 subscales. Specifically, Anglo and African American homeless adults had greater functional impairment than did Latino or Native American respondents. In addition, high Anglo orientation among chronically homeless Latino respondents, with low ethnic identity was associated with higher levels of functional impairment on the BASIS-32 Psychosis subscale. The implications of these findings are discussed.