diff --git a/README.md b/README.md
index 250a009..cfc84c6 100644
--- a/README.md
+++ b/README.md
@@ -71,11 +71,11 @@ algorithm and setting may vary. The following list gives the recommended
 settings:
 
 * Illumina/454/IonTorrent single-end reads longer than ~70bp or assembly
-  contigs up to a few megabases mapped to a close related reference genome:
+  contigs up to a few megabases mapped to a closely related reference genome:
 
 		bwa mem ref.fa reads.fq > aln.sam
 
-* Illumina single-end reads no longer than ~70bp:
+* Illumina single-end reads shorter than ~70bp:
 
 		bwa aln ref.fa reads.fq > reads.sai; bwa samse ref.fa reads.sai reads.fq > aln-se.sam
 
@@ -83,24 +83,21 @@ settings:
 
 		bwa mem ref.fa read1.fq read2.fq > aln-pe.sam
 
-* Illumina paired-end reads no longer than ~70bp:
+* Illumina paired-end reads shorter than ~70bp:
 
 		bwa aln ref.fa read1.fq > read1.sai; bwa aln ref.fa read2.fq > read2.sai
 		bwa sampe ref.fa read1.sai read2.sai read1.fq read2.fq > aln-pe.sam
 
-* PacBio subreads to a reference genome:
+* PacBio subreads or Oxford Nanopore reads to a reference genome:
 
 		bwa mem -x pacbio ref.fa reads.fq > aln.sam
-
-* Oxford Nanopore reads to a reference genome:
-
 		bwa mem -x ont2d ref.fa reads.fq > aln.sam
 
 BWA-MEM is recommended for query sequences longer than ~70bp for a variety of
 error rates (or sequence divergence). Generally, BWA-MEM is more tolerant with
 errors given longer query sequences as the chance of missing all seeds is small.
-As is shown above, with non-default settings, BWA-MEM works with PacBio subreads
-with a sequencing error rate as high as ~15%.
+As is shown above, with non-default settings, BWA-MEM works with Oxford Nanopore
+reads with a sequencing error rate over 20%.
 
 ####<a name="multihit"></a>2. Why does a read appear multiple times in the output SAM?
 
diff --git a/bwa.c b/bwa.c
index 495b197..e2e1376 100644
--- a/bwa.c
+++ b/bwa.c
@@ -259,12 +259,80 @@ bwaidx_t *bwa_idx_load(const char *hint, int which)
 void bwa_idx_destroy(bwaidx_t *idx)
 {
 	if (idx == 0) return;
-	if (idx->bwt) bwt_destroy(idx->bwt);
-	if (idx->bns) bns_destroy(idx->bns);
-	if (idx->pac) free(idx->pac);
+	if (idx->mem == 0) {
+		if (idx->bwt) bwt_destroy(idx->bwt);
+		if (idx->bns) bns_destroy(idx->bns);
+		if (idx->pac) free(idx->pac);
+	} else free((uint8_t*)idx->mem);
 	free(idx);
 }
 
+int bwa_mem2idx(int64_t l_mem, const uint8_t *mem, bwaidx_t *idx)
+{
+	int64_t k = 0, x;
+	int i;
+
+	// generate idx->bwt
+	x = sizeof(bwt_t); idx->bwt = (bwt_t*)(mem + k); k += x;
+	x = idx->bwt->n_sa * sizeof(bwtint_t); idx->bwt->sa = (bwtint_t*)(mem + k); k += x;
+	x = idx->bwt->bwt_size * 4; idx->bwt->bwt = (uint32_t*)(mem + k); k += x;
+
+	// generate idx->bns and idx->pac
+	x = sizeof(bntseq_t); idx->bns = (bntseq_t*)(mem + k); k += x;
+	x = idx->bns->n_holes * sizeof(bntamb1_t); idx->bns->ambs = (bntamb1_t*)(mem + k); k += x;
+	x = idx->bns->n_seqs  * sizeof(bntann1_t); idx->bns->anns = (bntann1_t*)(mem + k); k += x;
+	for (i = 0; i < idx->bns->n_seqs; ++i) {
+		idx->bns->anns[i].name = (char*)(mem + k); k += strlen(idx->bns->anns[i].name) + 1;
+		idx->bns->anns[i].anno = (char*)(mem + k); k += strlen(idx->bns->anns[i].anno) + 1;
+	}
+	idx->pac = (uint8_t*)(mem + k);
+
+	idx->l_mem = k; idx->mem = mem;
+	return 0;
+}
+
+int bwa_idx2mem(bwaidx_t *idx)
+{
+	int i;
+	int64_t k = 0, x, tmp;
+	uint8_t *mem = 0;
+
+	// copy idx->bwt
+	mem = malloc(sizeof(bwt_t) + idx->bwt->n_sa * sizeof(bwtint_t));
+	x = sizeof(bwt_t); memcpy(mem + k, idx->bwt, x); k += x;
+	x = idx->bwt->n_sa * sizeof(bwtint_t); memcpy(mem + k, idx->bwt->sa, x); k += x;
+	free(idx->bwt->sa);
+	mem = realloc(mem, k + idx->bwt->bwt_size * 4);
+	x = idx->bwt->bwt_size * 4; memcpy(mem + k, idx->bwt->bwt, x); k += x;
+	free(idx->bwt->bwt);
+	free(idx->bwt); idx->bwt = 0;
+
+	// copy idx->bns
+	tmp = idx->bns->n_seqs * sizeof(bntann1_t) + idx->bns->n_holes * sizeof(bntamb1_t);
+	for (i = 0; i < idx->bns->n_seqs; ++i) // compute the size of heap-allocated memory
+		tmp += strlen(idx->bns->anns[i].name) + strlen(idx->bns->anns[i].anno) + 2;
+	mem = realloc(mem, k + sizeof(bntseq_t) + tmp);
+	x = sizeof(bntseq_t); memcpy(mem + k, idx->bns, x); k += x;
+	x = idx->bns->n_holes * sizeof(bntamb1_t); memcpy(mem + k, idx->bns->ambs, x); k += x;
+	free(idx->bns->ambs);
+	x = idx->bns->n_seqs * sizeof(bntann1_t); memcpy(mem + k, idx->bns->anns, x); k += x;
+	for (i = 0; i < idx->bns->n_seqs; ++i) {
+		x = strlen(idx->bns->anns[i].name) + 1; memcpy(mem + k, idx->bns->anns[i].name, x); k += x;
+		x = strlen(idx->bns->anns[i].anno) + 1; memcpy(mem + k, idx->bns->anns[i].anno, x); k += x;
+		free(idx->bns->anns[i].name); free(idx->bns->anns[i].anno);
+	}
+	free(idx->bns->anns);
+
+	// copy idx->pac
+	x = idx->bns->l_pac/4+1;
+	mem = realloc(mem, k + x);
+	memcpy(mem + k, idx->pac, x); k += x;
+	free(idx->bns); idx->bns = 0;
+	free(idx->pac); idx->pac = 0;
+
+	return bwa_mem2idx(k, mem, idx);
+}
+
 /***********************
  * SAM header routines *
  ***********************/
diff --git a/bwa.h b/bwa.h
index bbc2525..7e2c153 100644
--- a/bwa.h
+++ b/bwa.h
@@ -14,6 +14,9 @@ typedef struct {
 	bwt_t    *bwt; // FM-index
 	bntseq_t *bns; // information on the reference sequences
 	uint8_t  *pac; // the actual 2-bit encoded reference sequences with 'N' converted to a random base
+
+	int64_t l_mem;
+	const uint8_t *mem;
 } bwaidx_t;
 
 typedef struct {
@@ -39,6 +42,8 @@ extern "C" {
 
 	bwaidx_t *bwa_idx_load(const char *hint, int which);
 	void bwa_idx_destroy(bwaidx_t *idx);
+	int bwa_idx2mem(bwaidx_t *idx);
+	int bwa_mem2idx(int64_t l_mem, const uint8_t *mem, bwaidx_t *idx);
 
 	void bwa_print_sam_hdr(const bntseq_t *bns, const char *rg_line);
 	char *bwa_set_rg(const char *s);
diff --git a/main.c b/main.c
index 77cace1..9108c49 100644
--- a/main.c
+++ b/main.c
@@ -4,7 +4,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.7.10-r896-dirty"
+#define PACKAGE_VERSION "0.7.10-r898-dirty"
 #endif
 
 int bwa_fa2pac(int argc, char *argv[]);