Summary Many algae are auxotrophs for vitamin B12 (cobalamin), which they need as a cofactor for B12‐dependent methionine synthase (METH). Because only prokaryotes can synthesize the cobalamin, they must be the ultimate source of the vitamin. In the laboratory, a direct interaction between algae and heterotrophic bacteria has been shown, with bacteria supplying cobalamin in exchange for fixed carbon. Here we establish a system to study this interaction at the molecular level. In a culture of a B12‐dependent green alga Chlamydomonas nivalis, we found a contaminating bacterium, identified by 16S rRNA analysis as Mesorhizobium sp. Using the sequenced strain of M. loti (MAFF303099), we found that it was able to support the growth of B12‐dependent Lobomonas rostrata, another green alga, in return for fixed carbon. The two organisms form a stable equilibrium in terms of population numbers, which is maintained over many generations in semi‐continuous culture, indicating a degree of regulation. However, addition of either vitamin B12 or a carbon source for the bacteria perturbs the equilibrium, demonstrating that the symbiosis is mutualistic and facultative. Chlamydomonas reinhardtii does not require B12 for growth because it encodes a B12‐independent methionine synthase, METE, the gene for which is suppressed by addition of exogenous B12. Co‐culturing C. reinhardtii with M. loti also results in reduction of METE expression, demonstrating that the bacterium can deliver the vitamin to this B12‐independent alga. We discuss the implications of this for the widespread distribution of cobalamin auxotrophy in the algal kingdom.

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Purpose – The purpose of this paper is to discuss several cultural and psychological aspects that the author experienced in the interview fieldwork with Vietnamese and the strategies to deal with these methodological issues. It aims to assist non-Vietnamese researchers planning their qualitative fieldwork with Vietnamese participants. Design/methodology/approach – The results are drawn from using an autoethnographic approach, in which the author presents and analyses the experiences of conducting individual semi-structured interviews with 15 Vietnamese college teachers in the PhD qualitative study on the Vietnamese concept of face – thê diên. Findings – The author argues that in interviews with Vietnamese participants, an interviewer should be mindful of the interviewees’ unfamiliarity with the ethics approval procedure, their reliance on relationship and trust, their self-face concern and low level of elaboration. It is important that the interviewer be seen as an “insider” by the Vietnamese interviewees, not an “objective” outsider researcher. In addition, an interviewer needs to be sensitive to detect any subtle cues that may emerge, and be flexible enough to adjust the interview questions if necessary and employ suitable techniques to adapt to these changes. Research limitations/implications – The findings were limited to the scope of experiences within a PhD study with a small group of college teachers. Experiences with larger groups of Vietnamese participants from diverse backgrounds may be needed to confirm the findings of this paper. Originality/value – This paper addresses the gap in the discussion of conducting qualitative research with the Vietnamese. It also discusses several issues that have not been discussed before, such as the Vietnamese unfamiliarity with the paperwork required for ethics approval and their face concerns in interviews.

In an East Asian context heavily influenced by Confucian ideas on principles for living and behaving, 'face' plays a significant role in Vietnamese people's thinking and behaviour. In the context of education, Vietnamese teachers' concerns of saving face in classrooms have been implicitly taken for granted but not yet seriously examined in academic research. The paper addresses this gap in the research literature by presenting the results of interviews with 15 lecturers in a Vietnamese Teacher Training College. It is argued that the concepts of face and saving face are significant to the participants and their ideas of saving face are largely influenced by traditional Confucian standards in education. In particular, teachers are believed to save face by upholding the belief that they represent an unquestionable source of knowledge, maintaining a 'noble distant image' in relations with their students, and receiving respectful behaviours from their students. These beliefs could be one source of resistance to educational reforms regarding interactive pedagogies in Vietnamese higher education. It is argued that teachers' concerns of saving face in Vietnamese classrooms deserve more attention from educational planners and researchers.

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